opinion: Mr. Justice Clark
  delivered the opinion of the Court.
  The question here is whether mandamus is an appropriate remedy to vacate a severance and transfer order entered by a district judge on the ground of improper venue, under 28 U. S. C. § 1406 (a).
  This case arises out of a treble damage action brought by petitioner, an Illinois insurance corporation, in the United States District Court for the Southern District of Florida, alleging a conspiracy to injure petitioner’s business, in violation of the Sherman and Clayton Acts. The complaint named as defendants the insurance commissioners of Georgia and Florida, one other individual, and four insurance companies residing and transacting business in the Southern District of Florida. The Georgia insurance commissioner, Cravey, was personally served in the Northern District of Florida and, without entering his appearance or waiving venue, moved to quash the summons and return of service and dismiss him from the action for improper venue.
  The applicable venue statute for private treble damage actions brought under the antitrust laws, 15 U. S. C. § 15, allows suit “in any district court of the United States in the district in which the defendant resides or is found or has an agent . . . .” It is admitted that Commissioner Cravey was not a resident of the Southern District of Florida, but petitioner contends that the Commissioner “was a member of a conspiracy whose other members were residing and carrying on the illegal business of the conspiracy in the Southern District of Florida, . . . that a conspiracy is a partnership and that co-conspirators are each other’s agents ...” and that the Commissioner therefore was “found” and had “agents” in the district, within the meaning of the statute. In furtherance of its theory that the Commissioner was “found” in the district, petitioner alleged overt acts committed by the Commissioner, as well as his codefendants, in the district where the suit was filed. The respondent judge held that the court had jurisdiction of the action and of the Commissioner, under Rule 4 (f) of the Rules of Civil Procedure, service of process having been had on him in the Northern District of Florida. The judge held, however, that venue was not properly laid and, pursuant to 28 U. S. C. § 1406 (a), ordered the action as to Cravey severed and transferred to the Northern District of Georgia where Cravey resided. Petitioner then sought a writ of mandamus from the Court of Appeals to compel the respondent to vacate and set aside the order of severance and transfer. The Court of Appeals dismissed the petition for mandamus on the ground that it was not an appropriate remedy. 199 F. 2d 593. Because of the importance of the question in the effective administration of federal law we granted certio-rari. 345 U. S. 933.
  At the outset it appears to be agreed that the District Court had jurisdiction over Commissioner Cravey under the process served on him in the Northern District of Florida. However, petitioner contends that the respondent judge had “power” to order the severance and transfer only if venue was improperly laid and that when venue is proper that “power” does not exist. Petitioner insists that venue was proper on the theory aforesaid that the Commissioner was “found” or had “agents” in the district ; that the severance and transfer order was therefore void but being interlocutory no appeal would lie; and that the only effective remedy is mandamus. While it admits that the order eventually may be reviewed on appeal from final judgment in the case, petitioner contends that insurmountable procedural difficulties requiring appeals from, and reversals of, the final judgments in both the Florida action and the severed action in Georgia render that remedy speculative, ineffective and inadequate in preventing needless expense, hardship and judicial inconvenience. Wherefore, it says, the extraordinary writ of mandamus is appropriate.
  We are of the opinion that in the circumstances of this case the writ was inappropriate.
  The All Writs Act grants to the federal courts the power to issue “all writs necessary or appropriate in aid of their respective jurisdictions and agreeable to the usages and principles of law.” 28 U. S. C. § 1651 (a). As was pointed out in Roche v. Evaporated Milk Assn., 319 U. S. 21, 26 (1943), the “traditional use of the writ in aid of appellate jurisdiction both at common law and in the federal courts has been to confine an inferior court to a lawful exercise of its prescribed jurisdiction or to compel it to exercise its authority when it is its duty to do so.” Here, however, petitioner admits that the court had jurisdiction both of the subject matter of the suit and of the person of Commissioner Cravey and that it was necessary in the due course of the litigation for the respondent judge to rule on the motion. The contention is that in acting on the motion and ordering transfer he exceeded his legal powers and this error ousted him of jurisdiction. But jurisdiction need not run the gauntlet of reversible errors. The ruling on a question of law decisive of the issue presented by Cravey’s motion and the replication of the petitioner was made in the course of the exercise of the court’s jurisdiction to decide issues properly brought before it. Ex parte American Steel Barrel Co., 230 U. S. 35, 45-46 (1913); Ex parte Roe, 234 U. S. 70, 73 (1914). Its decision against petitioner, even if erroneous — which we do not pass upon — involved no abuse of judicial power, Roche v. Evaporated Milk Assn., supra, and is reviewable upon appeal after final judgment. If we applied the reasoning advanced by the petitioner, then every interlocutory order which is wrong might be reviewed under the All Writs Act. The office of a writ of mandamus would be enlarged to actually control the decision of the trial court rather than used in its traditional function of confining a court to its prescribed jurisdiction. In strictly circumscribing piecemeal appeal, Congress must have realized that in the course of judicial decision some interlocutory orders might be erroneous. The supplementary review power conferred on the courts by Congress in the All Writs Act is meant to be used only in the exceptional case where there is clear abuse of discretion or “usurpation of judicial power” of the sort held to justify the writ in De Beers Consolidated Mines v. United States, 325 U. S. 212, 217 (1945). This is not such a case.
  It is urged, however, that the use of the writ of mandamus is appropriate here to prevent “judicial inconvenience and hardship” occasioned by appeal being delayed until after final judgment. But it is established that the extraordinary writs cannot be used as substitutes for appeals, Ex parte Fahey, 332 U. S. 258, 259-260 (1947), even though hardship may result from delay and perhaps unnecessary trial, United States Alkali Export Assn. v. United States, 325 U. S. 196, 202-203 (1945); Roche v. Evaporated Milk Assn., supra, at 31; and whatever may be done without the writ may not be done with it. Ex parte Rowland, 104 U. S. 604, 617 (1882). We may assume that, as petitioner contends, the order of transfer defeats the objective of trying related issues in a single action and will give rise to a myriad of legal and practical problems as well as inconvenience to both courts; but Congress must have contemplated those conditions in providing that only final judgments are reviewable. Petitioner has alleged no special circumstances such as were present in the cases which it cites. Furthermore, whatever “judicial inconvenience and hardship” may exist here will remain, after transfer, within the realm of the same court of appeals which has denied the writ, since both of the districts are within that circuit; and it is not clear that adequate remedy cannot be afforded petitioner in due course by that court to prevent some of the conflicts and procedural problems anticipated.
  We note additionally that the petitioner has not met the burden of showing that its right to issuance of the writ is “clear and indisputable.” United States v. Duell, 172 U. S. 576, 582 (1899). While a criminal action under the antitrust laws lies in any district where the conspiracy was formed or in part carried on or where an overt act was committed in furtherance thereof, Congress by 15 U. S. C. § 15 placed definite limits on venue in treble damage actions. Certainly Congress realized in so doing that many such cases would not lie in one district as to all defendants, unless venue was waived. It must, therefore, have contemplated that such proceedings might be severed and transferred or filed in separate districts originally. Thus petitioner’s theory has all the earmarks of a frivolous albeit ingenious attempt to expand the statute.
  We adhere to the language of this Court in Ex parte Fahey, supra, at 259-260:
  “Mandamus, prohibition and injunction against judges are drastic and extraordinary remedies. We do not doubt power in a proper case to issue such writs. But they have the unfortunate consequence of making the judge a litigant, obliged to obtain personal counsel or to leave his defense to one of the litigants before him. These remedies should be resorted to only where appeal is a clearly inadequate remedy. ... As extraordinary remedies, they are reserved for really extraordinary causes.”
  Affirmed.
  Mr. Justice Douglas concurs in the result.
  “The district court of a district in which is filed a case laying venue in the wrong division or district shall dismiss, or if it be in the interest of justice, transfer such case to any district or division in which it could have been brought.”
  Rule 4 (f) of Rules of Civil Procedure:
  “Territorial Limits of Effective Service. All process other than a subpoena may be served anywhere within the territorial limits of the state in which the district court is held and, when a statute of the United States so provides, beyond the territorial limits of that state. A subpoena may be served within the territorial limits provided in Rule 45.”
  See Gulf Research & Development Co. v. Leahy, 193 F. 2d 302 (1951).
  28 U. S. C. §§ 1291, 1292.
  Ex parte Simons, 247 U. S. 231 (1918); United States Alkali Export Assn. v. United States, supra; De Beers Consolidated Mines v. United States, supra. See also Ex parte United States, 287 U. S. 241 (1932); Maryland v. Soper, 270 U. S. 9 (1926).
  United States v. Trenton Potteries Co., 273 U. S. 392, 402-403 (1927); United States v. Socony-Vacuum Oil Co., 310 U. S. 150, 252-253 (1940).
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