During the past 20 years, we have treated 250 previously untreated adults (greater than age 15 years) with acute lymphoblastic leukemia (ALL) with five successive multidrug protocols: L2, L10, L10M, L17/17M, and L20. The L10 and L10M protocols had the highest percentage of long-term (greater than 5 years) remissions (52% and 40% respectively) compared with the L2 and more recent protocols (24%-32%); this is partly attributable to a greater prevalence of adverse risk factors among the latter protocols. The overall long-term survival of the first 199 patients with minimum 3 years follow-up is now 31%, with 35% of the 163 patients achieving complete remission (CR) remaining free of relapse for greater than 5 years. The disease-free survival of the 163 patients reaches a plateau of 33% after 6 years. The percentages of patients subsequently relapsing after remaining in continuous CR for 1.5, 3, and 5 years are 42%, 28%, and 6%, respectively; no relapses have yet occurred after 6 years in this series. Postrelapse survival improved progressively with longer duration of first remission. The results of treatment in second or later remission with either chemotherapy or bone marrow transplantation (BMT) were unsatisfactory and there were only a few long-term survivors. Recently we have attempted to select patients at highest risk of early relapse for BMT in first remission, but the number of eligible patients actually having BMTs has been low for a variety of reasons, including early death, failure to reach CR, early relapse, patient refusal, or medical contraindications.(ABSTRACT TRUNCATED AT 250 WORDS)