Fifty-four patients with ovarian cancer who achieved a complete or partial remission with cisplatin or carboplatin were rechallenged with the same drug or crossed over to the other platinum compound at relapse. Fifteen of 43 (35%) crossover patients and 1/11 (9%) rechallenged patients responded; the difference was not significant and there was no difference in survival between the two groups. Responders survived significantly longer than nonresponders (P = 0.001) but there was no survival difference between those who responded to a rechallenge and those who responded to crossing over to the other platinum compound. The progression-free interval between the end of initial treatment and relapse was a significant prognostic factor for response to treatment and survival; 17% (6/35) of patients who relapsed before 18 months responded as compared to 53% (10/19) who relapsed after 18 months (P = 0.006) and median survival was 221 and 486 days, respectively, for these two groups (P = 0.026).