The case histories of 252 adolescent and adult patients with acute leukemia diagnosed and treated between 1975 and 1985 are analyzed with special attention to prognostic factors determining the second complete remission (CR) rate. A first CR was achieved in 65% of cases, 60% for acute myelogenous leukemia (AML), and 75% for lymphoblastic leukemia (ALL). In 86 patients a relapse occurred (50 AML, 36 ALL), and 50% of them entered a second CR after reinduction therapy. Median survival after first relapse of these reinduction-responders was significantly prolonged in comparison to the reinduction-nonresponders for both AML (15 versus 2 months) and ALL (11 versus 3 months). Median duration of the first CR of the reinduction-responders was significantly longer than that of the second CR (13 versus 6 months). The major determinant for the probability to obtain a second CR after reinduction therapy was the duration of the first CR. The latter was significantly longer in the reinduction-responders than in the nonresponding group (13 versus 5 months). Furthermore patients younger than 40 years, and those who relapsed after ending the maintenance therapy, tended to have better chances to achieve a second CR. Rapid achievement of the first CR, and sex of the patients seemed not to be of predictive value. The authors conclude that aiming for a second CR is worthwhile in young patients who relapse after a long first CR.