Aclarubicin was evaluated in combination chemotherapy for adult acute myeloid leukemia in a randomized trial involving 58 institutions throughout Japan. Behenoyl cytosine arabinoside (BH-AC).daunorubicin, 6-mercaptopurine, and prednisolone (DMP) was compared with BH-AC.aclarubicin, 6-mercaptopurine, and prednisolone (AMP). In the 360 evaluable cases among the 433 cases enrolled, complete remission (CR) rates were 63.7% (116/182) for BH-AC.DMP and 53.9% (96/178) for BH-AC.AMP (P = 0.0587). Median survival periods and 7-year survival rates were 15.8 months and 19.3% for BH-AC.DMP and 9.5 months and 20.2% for BH-AC.AMP (P = 0.0091 according to the generalized Wilcoxon test [GW], P = 0.196 according the log-rank test [LR]). Median disease-free survival periods were 15.4 months for BH-AC.DMP and 14.1 months for BH-AC.AMP (P = 0.851 by GW, P = 0.439 by LR). Among the 346 cases of extramurally confirmed FAB subtypes, CR rates were 67.9% (19/28) with BH-AC.DMP and 31.8% (7/22) with BH-AC.AMP for subtype M3 (P = 0.011) and 63.3% (93/147) with BH-AC.DMP and 56.8% (84/148) with BH-AC.AMP (P = 0.254) for subtypes M1, M2, M4, and M5. Diarrhea, ileus, pneumonia, and renal failure were more frequent with BH-AC.AMP than with BH-AC.DMP. The results indicate, at least on the basis of the long-term outcome, that BH-AC.AMP has antileukemic effects on subtypes M1, M2, M4, and M5 that are comparable with those of BH-AC.DMP.