Justice O’Connor
delivered the opinion of the Court.
The Sentencing Reform Act of 1984 (Act), as amended, 18 U.S.C. §3551 et seq., 28 U.S.C. §§991-998, created the United States Sentencing Commission and empowered it to promulgate guidelines establishing sentencing ranges for different categories of federal offenses and defendants. The Act permits a district court to depart from the presumptive sentencing range prescribed by the Sentencing Guidelines only in certain circumstances. 18 U. S. C. § 3553(b). The Act also provides for limited appellate review of sentences in order to ensure the proper application of the Guidelines. § 3742. In this case, we consider the scope of appellate review, under the Act, of a sentence in which a district court has departed from the guideline sentencing range.
I
Petitioner Joseph Williams, a previously convicted felon, was the subject of an investigation conducted by the Bureau of Alcohol, Tobacco and Firearms in 1988 and 1989. He was indicted and convicted after a jury trial in the United States District Court for the Western District of Wisconsin for possession of a firearm while a convicted felon in violation of 18 U.S. C. § 922(g)(1).
The presentence report assigned Williams a criminal history category of V. App. 48. Combined with an offense level of 9, the applicable sentencing range under the Guidelines was 18 to 24 months. Ibid. The District Court departed upward from this range pursuant to §4A1.3 of the Guidelines Manual, which allows a district court to increase a criminal history classification if “reliable information” indicates that the criminal history category does not adequately reflect the seriousness of the defendant’s criminal background or propensity for future criminal conduct. United States Sentencing Commission, Guidelines Manual §4A1.3, p. s. (Nov. 1991) (USSG). The District Court determined that Williams’ criminal history category was inadequate because it did not include two convictions that were too old to be counted in the Guidelines’ criminal history calculation, see §4A1.2(e)(l), and because it did not reflect several prior arrests. App. 53-54. Citing these two factors, the court looked to the next highest criminal history category, for which the guideline range was 21 to 27 months. Id., at 53-54. The court then sentenced Williams to 27 months’ imprisonment and explained that it was selecting a sentence at the high end of the guideline range because Williams had previously been convicted for the same offense and because he had threatened an undercover agent in this case. Id., at 55-56.
The United States Court of Appeals for the Seventh Circuit upheld the conviction and the sentence. 910 F. 2d 1574 (1990). It agreed with the District Court that, under the circumstances of this case, the two outdated convictions were “reliable information” indicating more extensive criminal conduct than was reflected by Williams’ criminal history category. Id., at 1579. It rejected, however, the District Court’s reliance upon Williams’ prior arrests not resulting in prosecution. Although the Guidelines allow a court to consider “prior similar adult criminal conduct not resulting in a criminal conviction” in determining whether a departure is warranted, they prohibit a court from basing a departure on a prior arrest record alone. USSG § 4A1.3, p. s. The Court of Appeals asserted that “the determination that the arrests indicated similar criminal conduct must be based on facts apart from the arrest record itself,” 910 F. 2d, at 1580, and held that the District Court had not adequately explained the factual basis for its use of Williams’ prior arrests as a ground for departure. Ibid.
Although it invalidated one of the two grounds mentioned by the District Court in its decision to depart, the Court of Appeals nevertheless affirmed Williams’ sentence. It relied upon the Seventh Circuit precedent of United States v. Franklin, 902 F. 2d 501 (CA7), cert. denied sub nom. Mann v. United States, 498 U. S. 906 (1990), which held that when a sentencing court uses both proper and improper factors to justify a departure, the sentence can be affirmed if it is reasonable in light of the proper factors standing alone. 902 F. 2d, at 508-509. Applying Franklin, the Court of Appeals concluded that, despite the District Court’s error in considering Williams’ prior arrest record, the court had “correctly determined that Mr. Williams’ criminality was not reflected properly in the criminal history category and that the relevant evidence justified the rather modest increase in sentence.” 910 F. 2d, at 1580.
We granted certiorari, 499 U. S. 918 (1991), to resolve a conflict among the Circuits on whether a reviewing court may affirm a sentence in which a district court’s departure from the guideline range is based on both valid and invalid factors. Compare United States v. Zamarripa, 905 F. 2d 337, 342 (CA10 1990) (when one or more of the stated grounds for departure is invalid, the case must be remanded for resentencing); United States v. Hernandez-Vasquez, 884 F. 2d 1314, 1315-1316 (CA9 1989) (same), with United States v. Franklin, supra, at 508-509 (when one or more of the stated grounds for departure is invalid, appellate court may affirm if sentence is still reasonable in light of remaining factors); United States v. Rodriguez, 882 F. 2d 1059, 1066-1068 (CA6 1989) (same), cert. denied, 493 U. S. 1084 (1990); United States v. Hummer, 916 F. 2d 186, 195, n. 8 (CA4 1990) (same), cert. denied, 499 U. S. 970 (1991).
II
The Act provides that a district court may depart from the sentencing range set by the Guidelines only when it finds that “there exists an aggravating or mitigating circumstance of a kind, or to a degree, not adequately taken into consideration by the Sentencing Commission in formulating the guidelines.” 18 U. S. C. § 3553(b). A defendant may file an appeal if a sentence was imposed in violation of law or as a result of an incorrect application of the Guidelines, or if the district court departed upward from the guideline range. § 3742(a). Similarly, the Government may file an appeal if a sentence was imposed in violation of law or as a result of an incorrect application of the Guidelines, or if the district court departed downward from the guideline range. § 3742(b).
For both types of appeal, § 3742(f) delineates the following narrow scope of review:
“If the court of appeals determines that the sentence—
“(1) was imposed in violation of law or imposed as a result of an incorrect application of the sentencing guidelines, the court shall remand the case for further sentencing proceedings with such instructions as the court considers appropriate;
“(2) is outside the applicable guideline range and is unreasonable or was imposed for an offense for which there is no applicable sentencing guideline and is plainly unreasonable, it shall state specific reasons for its conclusions and—
“(A) if it determines that the sentence is too high and the appeal has been filed [by the defendant], it shall set aside the sentence and remand the case for further sentencing proceedings with such instructions as the court considers appropriate;
“(B) if it determines that the sentence is too low and the appeal has been filed [by the Government], it shall set aside the sentence and remand the case for further sentencing proceedings with such instructions as the court considers appropriate;
“(3) is not described in paragraph (1) or (2), it shall affirm the sentence.”
A
In the case before us, Williams urges that the District Court’s use of his arrest record as a ground for departure was a misapplication of the Guidelines and that the “incorrect application” standard of § 3742(f)(1) means that once a departure ground is invalidated, a remand is always in order. The Government does not dispute that a district court’s reliance upon an invalid factor in departing from- the guideline sentencing range is appropriately characterized as an “incorrect application” of the Guidelines, but contends that a remand is only required when the error was. determinative in the decision to depart.
We agree with both parties that a sentencing court’s use of an invalid departure ground is an incorrect application of the Guidelines. The Guidelines echo the Act’s instruction that a district court may depart from the applicable guideline range only when it finds an aggravating or mitigating circumstance “‘not adequately taken into consideration by the Sentencing Commission’ ” in formulating the Guidelines. USSG § lA4(b), p. s., § 5K2.0, p. s. (both quoting 18 U. S. C. § 3553(b)). Construing the plain language of the Guidelines Manual and the governing statute, we conclude that it is an incorrect application of the Guidelines for a district court to depart from the applicable sentencing range based on a factor that the Commission has- already fully considered in establishing the guideline range or, as in this case, on a factor that the Commission has expressly rejected as an appropriate ground for departure.
Congress has defined “guidelines” as “the guidelines promulgated by the commission pursuant to section 994(a).” 28 U. S. C. § 998(c). Section 994(a) grants the Commission the authority to promulgate both “guidelines,” § 994(a)(1), and “general policy statements regarding application of the guidelines,” § 994(a)(2). The dissent draws a distinction between the “actual” guidelines and the policy statements that “interpret” and “explain]” them; in the dissent’s view, only the former can be incorrectly applied within the meaning of 18 U. S. C. § 3742(f)(1). Post, at 211-212. But to say that guidelines are distinct from policy statements is not to say that their meaning is unaffected by policy statements. Where, as here, a policy statement prohibits a district court from taking a specified action, the statement is an authoritative guide to the meaning of the applicable Guideline. An error in interpreting such a policy statement could lead to an incorrect determination that a departure was appropriate. In that event, the resulting sentence would be one that was “imposed as a result of an incorrect application of the sentencing guidelines” within the meaning of § 3742(f)(1). Similarly, an erroneous calculation under the Sentencing Table, from which all Guidelines sentencing ranges are derived, could properly be reviewed as an “incorrect application of the sentencing guidelines” under § 3742(f)(1) even though the Table itself is not officially designated as a “guideline.” See USSG ch. 5, pt. A.
Because use of a departure ground prohibited by a policy statement can be an “incorrect application” of the Guidelines under § 3742(f)(1), we also agree with both Williams and the Government that, when a district court relies upon an improper ground in departing from the guideline range, a reviewing court may not affirm a sentence based solely on its independent assessment that the departure is reasonable under § 3742(f)(2). Section 3742(f) specifies two circumstances in which a court of appeals must remand for resen-tencing: if the sentence was imposed as a result of an incorrect application of the Guidelines or if the sentence is an unreasonable departure from the applicable guideline range. The statute does not allow a court to focus on one remand provision to the exclusion of the other.
We do not believe that the dissent’s contrary conclusion is supported by declarations from Congress and the Sentencing Commission which state that departure sentences are reviewable under § 3742(f)(2). Post, at 209-210, 212-213. We are unable to find any indication in those statements that departures from the Guidelines are to be reviewed exclusively under § 3742(f)(2). Thus, we believe that, while departure decisions are properly reviewed under § 3742(f)(2), they are also properly reviewed under § 3742(f)(1) when they are the result of an incorrect application of the Guidelines (considered in light of the relevant policy statements) that govern departure decisions. In order to give full effect to both provisions, therefore, the reviewing court is obliged to conduct two separate inquiries. First, was the sentence imposed either in violation of law or as a result of an incorrect application of the Guidelines? If so, a remand is required under § 3742(f)(1). If the court concludes that the departure is not the result of an error in interpreting the Guidelines, it should proceed to the second step: is the resulting sentence an unreasonably high or low departure from the relevant guideline range? If so, a remand is required under § 3742(f)(2).
Williams argues further that whenever a court of appeals finds that a district court considered an erroneous factor in sentencing, a remand is automatically required under § 3742(f)(1) in order to rectify an “incorrect application” of the Guidelines. We disagree. Section 3742(f)(1) does not call for a remand every time a sentencing court might misapply a provision of the Guidelines; rather, remand is required only if the sentence was “imposed as a result of an incorrect application” of the Guidelines. When a district court has not intended to depart from the Guidelines, a sentence is imposed “as a result of” an incorrect application of the Guidelines when the error results in the district court selecting a sentence from the wrong guideline range. When a district court has intended to depart from the guideline range, a sentence is imposed “as a result of” a misapplication of the Guidelines if the sentence would have been different but for the district court’s error. Accordingly, in determining whether a remand is required under § 3742(f)(1), a court of appeals must decide whether the district court would have imposed the same sentence had it not relied upon the invalid factor or factors.
We conclude that the party challenging the sentence on appeal, although it bears the initial burden of showing that the district court relied upon an invalid factor at sentencing, does not have the additional burden of proving that the invalid factor was determinative in the sentencing decision. Rather, once the court of appeals has decided that the district court misapplied the Guidelines, a remand is appropriate unless the reviewing court concludes, on the record as a whole, that the error was harmless, i. e., that the error did not affect the district court’s selection of the sentence imposed. See Fed. Rule Crim. Proc. 52(a).
B
If the party defending the sentence persuades the court of appeals that the district court would have imposed the same sentence absent the erroneous factor, then a remand is not required under § 3742(f)(1), and the court of appeals may affirm the sentence as long as it is also satisfied that the departure is reasonable under § 3742(f)(2). The reasonableness determination looks to the amount and extent of the departure in light of the grounds for departing. In assessing reasonableness under § 3742(f)(2), the Act directs a court of appeals to examine the factors to be considered in imposing a sentence under the Guidelines, as well as the district court’s stated reasons for the imposition of the particular sentence. § 3742(e). A sentence thus can be “reasonable” even if some of the reasons given by the district court to justify the departure from the presumptive guideline range are invalid, provided that the remaining reasons are sufficient to justify the magnitude of the departure.
C
The dissent interprets the “reasonableness” standard of § 3742(f)(2) to be the sole provision governing appellate review of departure decisions. The dissent also posits a two-step test of reasonableness: the appellate court must determine the reasonableness of the district' court’s decision to depart based on the court’s stated reasons for departure, post, at 218, and the appellate court must determine the reasonableness of the amount or extent of departure, post, at 218-220. This is similar to our two-step inquiry, see supra, at 201-202, for determining when a remand is required. The dissent thus agrees that “[w]here all the reasons enunciated by the district court to support departure are found to be invalid,” the appellate court “must set aside the sentence and remand the case,” post, at 218, although it would find such a remand necessary because “the departure is per se unreasonable,” ibid., and not because it was imposed “as a result of” an incorrect application of the Guidelines. When some but not all of the district court’s reasons for departure are invalid, however, the dissent’s position requires the appellate court to consider whether the district court could have based its departure on the remaining factors, post, at 219, and not whether it would still have chosen so to act, supra, at 203.
In practical effect, therefore, the divergence of the dissent’s interpretation of the statute from our own is in the degree of an appellate court’s authority to affirm a sentence when the district court, once made aware of the errors in its interpretation of the Guidelines, may have chosen a different sentence. Although the Act established a limited appellate review of sentencing decisions, it did not alter a court of appeals’ traditional deference to a district court’s exercise of its sentencing discretion. The selection of the appropriate sentence from within the guideline range, as well as the decision to depart from the range in certain circumstances, are decisions that are left solely to the sentencing court. USSG § 5K2.0, p. s. The development of the guideline sentencing regime has not changed our view that, except to the extent specifically directed by statute, “it is not the role of an appellate court to substitute its judgment for that of the sentencing court as to the appropriateness of a particular sentence.” Solem v. Helm, 463 U. S. 277, 290, n. 16 (1983).
Significantly, Congress amended the Act in 1986 to delete certain provisions that authorized an appellate court to correct a sentence determined to have been imposed as a result of an incorrect application of the Guidelines. See Criminal Law and Procedure Technical Amendments Act of 1986, § 73, 100 Stat. 3617. That action confirms our belief that it is the prerogative of the district court, not the court of appeals, to determine, in the first instance, the sentence that should be imposed in light of certain factors properly considered under the Guidelines.
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A
At oral argument in this Court, petitioner s counsel contended that both of the District Court’s stated grounds for departure were invalid and therefore that Williams’ sentence must have resulted from an incorrect application of the Guidelines. Tr. of Oral Arg. 42-43. Counsel argued that not only was it improper for the District Court to rely upon Williams’ prior arrest record, but also that the Guidelines prevented the court from considering convictions more than 16 years old. Id., at 43. The Guidelines explicitly authorize a district court to base a departure on outdated convictions that are “evidence of similar misconduct,” see USSG §4A1.2, comment., n. 8, but the Circuits are divided as to whether, by implication, they prohibit a departure based on nonsimi-lar outdated convictions. Compare, e. g., United States v. Aymelek, 926 F. 2d 64, 72-73 (CA1 1991) (nonsimilar outdated convictions may be appropriate grounds for departure); United States v. Russell, 905 F. 2d 1439, 1444 (CA10 1990) (same), with United States v. Leake, 908 F. 2d 550, 554 (CA9 1990) (upward departure can never be based on non-similar outdated convictions). In this case, the propriety of the District Court’s consideration of Williams’ nonsimilar outdated convictions was not clearly presented in the petition for certiorari and was not briefed by either party. Accordingly, we decline to review the Court of Appeals’ determination that Williams’ outdated convictions were reliable information that his criminal history category understated the extent of his criminal background. See 910 F. 2d, at 1578-1579.
B
The Court of Appeals was obliged to review, under both remand provisions of § 3742(f), a departure from the guideline range in which it found one of the two stated grounds for departure to be valid and the other to be invalid. We are unable to ascertain from its opinion whether the Court of Appeals concluded that the District Court would have imposed the same sentence even without relying upon Williams’ prior arrest record, see § 3742(f)(1), or whether it affirmed simply on the basis that the sentence was reasonable under § 3742(f)(2). We therefore vacate the judgment below affirming Williams’ sentence, and remand the case for a determination whether the sentence was imposed “as a result of” the District Court’s erroneous consideration of his prior arrests not resulting in prosecution.
It is so ordered.
Our reading of the sentencing transcript thus does not accord with the dissent’s understanding that the District Court also considered Williams’ prior conviction for the same offense in its decision to depart. See post, at 208.
The dissent states that an error in interpreting a policy statement governing departures “is not, in itself, subject to appellate review.” Post, at 212. The dissent believes that all departure decisions must be reviewed under the “reasonableness” standard of § 3742(f)(2) and that the “reasonableness” determination includes an assessment of whether the district court properly found an “ ‘aggravating or mitigating circumstance . ’. . not adequately taken into consideration by the Sentencing Commission in formulating the guidelines.’” Post, at 218 (quoting 18 U. S. C. §3553(b)). But, in determining whether a circumstance was adequately taken into consideration, a court must consider “the sentencing guidelines, policy statements, and official commentary of the Sentencing Commission.” § 3553(b). Thus, the dissent would appear to agree that an appellate court can review the validity of a district court’s reasons for departure for consistency with the Commission’s policy statements; it simply considers that inquiry to go to the “reasonableness” of the decision to depart rather than to the correct application of the Guidelines.