opinion: Mr. Justice Brennan
  delivered the opinion of the Court.
  The District Court for the Central District of California determined in 1973 that hiring practices of the County of Los Angeles respecting the County Fire Department violated 42 U. S. C. § 1981. The District Court in an unreported opinion and order permanently enjoined all future discrimination and entered a remedial hiring order. The Court of Appeals for the Ninth Circuit affirmed in part, reversed in part, and remanded the case for further consideration. 566 F. 2d 1334 (1977). We granted certiorari to consider questions presented as to whether the use of arbitrary employment criteria, racially exclusionary in operation, but not purposefully discriminatory, violates 42 U. S. C. § 1981 and, if so, whether the imposition of minimum hiring quotas for fully qualified minority applicants is an appropriate remedy in this employment discrimination case. 437 IT. S. 903 (1978). We now find that the controversy has become moot during the pend-ency of this litigation. Accordingly, we vacate the judgment of the Court of Appeals and direct that court to modify its remand so as to direct the District Court to dismiss the action.
  I
  In 1969, persons seeking employment with the Los Angeles County Fire Department were required to take a written civil service examination and a physical-agility test. Applicants were ranked according to their performance on the two tests and selected for job interviews on the basis of their scores. Those who passed their oral interviews were then placed on a hiring-eligibility list. Because blacks and Hispanics did poorly on the written examination, this method of screening job applicants proved to have a disparate impact on minority hiring.
  The County of Los Angeles has not used the written civil service examination as a ranking device since 1969. The county desisted, prior to the commencement of this litigation, because it felt that the test had a disparate adverse impact on minority hiring, because it feared that this impact might violate Title VII of the Civil Rights Act of 1964, 78 Stat. 253, as amended, 42 U. S. C. § 2000e et seq., and because it wished, in any event, to increase minority representation in the Fire Department. See App. to Brief for Respondents 1-4.
  In 1971, the county replaced the 1969 procedure with a new method of screening job applicants. A new written test was designed expressly to eliminate cultural bias. The test was to be given and graded on a pass-fail basis for the sole purpose of screening out illiterates. Five hundred of the passing applicants were to be selected at random for oral interviews and physical-agility tests. Passing applicants were to be ranked solely on the basis of the results of the physical-agility test and the oral interview. See 566 F. 2d, at 1346 (Wallace J., dissenting).
  An examination was conducted, pursuant to this plan, in January 1972. Ninety-seven percent of the applicants passed the written test. There was no disparate adverse impact on minorities and this use of the written examination has not been challenged in this litigation.
  After administration of the written test, but before the random selection could be made, an action was filed in state court against the county charging that the random-selection process violated provisions of the county charter and civil service regulations. The county was enjoined from using the random-selection method pending trial on the merits. See ibid.
  For a time the hiring process came to a halt. The eligibility list drawn from the 1969 examination had been exhausted. The county was unable to devise a nonrandom method of screening job applicants and the county lacked the resources to interview all of the applicants who had passed the 1972 examination.
  As a consequence of this unintended hiring freeze, vacancies in the County Fire Department increased and the manpower needs of the Department became critical. Finally, to break the logjam, the County Department of Personnel proposed to interview those applicants who had received the top 544 scores on the 1972 written test. Of this number, 492 were white, 10 black, and 33 Mexican-American. The applicants were not to be ranked on the basis of the test results, however, and the interviews were not intended to eliminate the remaining applicants from consideration. The purpose was solely to expedite the hiring of sufficient firefighters to meet the immediate urgent requirements of the Fire Department. See ibid. But when minority representatives objected to the plan, it was abandoned, uneffectuated, prior to the commencement of this litigation.
  In January 1973, respondents, representing present and future black and Mexican-American applicants to the Fire Department, brought a class action against the County of Los Angeles, the Board of Supervisors of the County of Los Angeles, and the Civil Service Commission of the County of Los Angeles (petitioners). Respondents charged that petitioners’ 1969 hiring procedures violated 42 U. S. C. § 1981. Respondents also charged that petitioners’ plan to interview those applicants who had received the top 544 scores on the 1972 written test violated 42 U. S. C. § 1981.
  The District Court found that petitioners had acted without discriminatory intent. Nonetheless, the District Court held that because the 1969 and 1972 written examinations had not been validated as predictive of job performance, petitioners’ employment practices had violated 42 U. S. C. § 1981. The court permanently enjoined all future discrimination and mandated good-faith affirmative-action efforts. The court also entered a remedial hiring order whereby at least 20% of all new firefighter recruits were required to be black and another 20% were required to be Mexican-American until the percentage of blacks and Mexican-Amerieans in the Los Angeles County Fire Department was commensurate with their percentage in Los Angeles County.'
  The Court of Appeals reversed the District Court with respect to the 1969 examination: The Court of Appeals held that respondents did not have standing to seek relief on account of the 1969 civil service examination because the plaintiff class, as certified by the District Court, consisted only of present and future job applicants and did not include any persons who had in any way been affected by the 1969 test.
  The Court of Appeals affirmed, however, the District Court’s holding with respect to the 1972 proposal to use ah unvalidated civil service examination.
  II
  The only question remaining in this case, then, concerns petitioners’ 1972 plan to interview the top 544 scorers on the 1972 written examination in order to fill temporary emergency manpower needs. We find that this controversy became moot during the pendency of this litigation.
  “Simply stated, a case is moot when the issues presented are no longer 'live’ or the parties lack a legally cognizable interest in the outcome.” Powell v. McCormack, 395 U. S. 486, 496 (1969). We recognize that, as a general rule, “voluntary cessation of allegedly illegal conduct does not deprive the tribunal of power to hear and determine the case, i. e., does not make the case moot.” United States v. W. T. Grant Co., 345 U. S. 629, 632 (1953). But jurisdiction, properly acquired, may abate if the case becomes moot because
  (1) it can be said with assurance that “there is no reasonable expectation . . .” that the alleged violation will recur, see id., at 633; see also SEC v. Medical Committee For Human Rights, 404 U. S. 403 (1972), and
  (2) interim relief or events have completely and irrevocably eradicated the effects of the alleged violation. See, e. g., DeFunis v. Odegaard, 416 U. S. 312 (1974); Indiana Employment Security Div. v. Burney, 409 U. S. 540 (1973).
  When both conditions are satisfied it may be said that the case is moot because neither party has a legally cognizable interest in the final determination of the underlying questions of fact and law.
  The burden of demonstrating mootness “is a heavy one.” See United States v. W. T. Grant Co., supra, at 632-633. Nevertheless, that burden is fully met on this record.
  The first condition is met because there can be no reasonable expectation that petitioners will use an unvalidated civil service examination for the purposes contemplated in 1972. Petitioners have not used an unvalidated written examination to rank job applicants since 1969. Petitioners considered employing such a procedure in 1972 only because of a temporary emergency shortage of firefighters and only because petitioners then had no alternative means of screening job applicants. Those conditions were unique, are no longer present, and are unlikely to recur because, since the commencement of this litigation, petitioners have succeeded in instituting an efficient and nonrandom method of screening job applicants and increasing minority representation in the Fire Department. The new procedures are as follows:
  To fill each group of vacancies petitioners interview 500 applicants who passed their written examination, including the highest scoring 300 whites, 100 blacks, and 100 Mexican-Americans. The number interviewed is several times the number of actual vacancies. The interviewers rate each of these applicants on his or her merits without regard to race or national origin. Thereafter applicants are hired solely on the basis of the score given by the interviewer, again without regard to race or national origin. Those hired are not hired from separate lists, no quotas are used, and the same rating standards are applied to all applicants. The interviewers are not authorized to give extra points because of an applicant’s race or national origin, but are directed only to be alert for talented minority applicants. This procedure has resulted every year since 1972 in a minority hiring level which consistently, though by varying amounts, exceeded 50%.
  There has been no suggestion by any of the parties, nor is there any reason to believe, that petitioners would significantly alter their present hiring practices if the injunction were dissolved. See also Brief for N. A. A. C. P. Legal Defense and Educational Fund, Inc., as Amicus Curiae 7. A fortiori, there is no reason to believe that petitioners would replace their present hiring procedures with procedures that they regarded as unsatisfactory even before the commencement of this litigation. Under these circumstances we believe that this aspect of the case has “lost its character as a present, live controversy of the kind that must exist if '[the Court is] to avoid advisory opinions on abstract propositions of law.” Hall v. Beals, 396 U. S. 45, 48 (1969).
  The second condition of mootness is met because petitioners’ compliance during the five years since 1973 with the District Court’s decree and their hiring of over 50% of new recruits from minorities has completely cured any discriminatory effects of the 1972 proposal. Indeed, it is extremely doubtful, from this record, that the 1972 proposal had any discriminatory effects to redress. The plan, it must be remembered, was never carried out. As a consequence, there has been no finding that any minority job applicant was excluded from employment as a result of the proposal. Cf. Franks v. Bowman Transportation Co., 424 U. S. 747 (1976). Nor has there been a finding that any prospective minority job applicant was deterred from applying for employment with the Fire Department as a result of the proposed application of the examination. Cf. Teamsters v. United States, 431 U. S. 324, 365-367 (1977). Nor has there been a finding that the 1972 proposal reflected a racial animus that might have tainted other employment practices. Cf. Keyes v. School Dist. No. 1, Denver, Colo., 413 U. S. 189 (1973). On the contrary the District Court expressly found:
  “Neither Defendants nor their officials engaged in employment practices with a willful or conscious purpose of excluding blacks and Mexican-Americans from employment at the Los Angeles County Fire Department. To the contrary, several of Defendants’ officials engaged in efforts designed to increase the minority representation in the Los Angeles County Fire Department.” App. 41.
  All of these circumstances, taken together, persuade us that, whatever might have been the case at the time of trial, the controversy has become moot during the pendency of this litigation. Accordingly, we vacate the judgment of the Court of Appeals and remand to that court for entry of an appropriate order directing the District Court to dismiss the action as moot. See United States v. Munsingwear, Inc., 340 U. S. 36, 39 (1960).
  So ordered.
  Revised Stat. § 1977, 42 U. S. C. § 1981, provides:
  “All persons within the jurisdiction of the United States shall have the same right in every State and Territory to make and enforce contracts, to sue, be parties, give evidence, and to the full and equal benefit of all laws and proceedings for the security of persons and property as is enjoyed by white citizens, and shall be subject to like punishment, pains, penalties, taxes, licenses, and exactions of every kind, and to no other.”
  Despite the fact that the Mexican-American population of Los Angeles County was approximately double the size of the black population, the District Court ordered identical accelerated hiring for both groups due to its finding that the Fire Department’s 5'7"' height requirement for job applicants was a valid requirement for employment and that this height requirement had the effect of eliminating 41% of the otherwise eligible Mexican-American applicants from consideration. See 566 F. 2d 1334, 1337 (1977). The Court of Appeals reversed the District Court in this respect and ordered a relative increase in the Mexican-American hiring quota. In light of our disposition on grounds of mootness we do not consider this issue.
  Respondents contend that their failure to include past applicants in the class was a “mere oversight” which should not be used to vitiate the District Court’s decree. But respondents did not cross petition for modification of the judgment of the Court of Appeals reversing the District Court with respect to the 1969 test. The issue of oversight, as a consequence, is not properly before us. See FEA v. Algonquin SNG, Inc., 426 U. S. 548, 560 n. 11 (1976). We intimate no view whether respondents may seek, despite the oversight, to bring a new lawsuit with new and proper parties. See Gibson v. Supercargoes & Checkers, 543 F. 2d 1259, 1264 (CA9 1976).
  The parties stipulated that approximately 100 vacancies occur in the ranks of firemen each year, and testimony at trial established that 187 applicants were placed on an eligibility list following the 1969 test. Based on this evidence the Court of Appeals concluded that the 1969 list had been exhausted before plaintiffs applied for employment as firefighters in October 1971. See 566 F. 2d, at 1338.
  Moreover, there appears to be no possibility that persons hired pursuant to the District Court’s order will be terminated in consequence of our vacation of the Court of Appeals’ judgment as moot. Cf. DeFunis v. Odegaard, 416 U. S. 312 (1974).
  Of necessity our decision “vacating the judgment of the Court of Appeals deprives that court’s opinion of precedential effect . . . .” O’Connor v. Donaldson, 422 U. S. 563, 577-578, n. 12 (1975). See also A. L. Mechling Barge Lines v. United States, 368 U. S. 324, 329-330 (1961).