Between March 1980 and December 1981, 22 patients were treated with 4'(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA) and 5-azacytidine (AZA), each given by I.V. push in a dosage of 150 mg/m2 for 5 days. Seven of 12 prior-remitting, acute nonlymphoblastic leukemia (ANLL) patients achieved complete remission (58%). Six ANLL patients who failed to remit on standard daunorubicin-cytosine arabinoside programs also failed to remit on the m-AMSA-AZA combination. Two patients with relapsed acute lymphatic leukemia (ALL) also failed while two patients with chronic myelocytic leukemia (CML) in evolution were cytoreduced. The seven patients who achieved remission had additional relapse-free survival for a median of six months (range 1-23+ months). One patient obtained a second remission with m-AMSA-AZA after relapse which followed a 9-month period of nonmaintained remission. Most patients demonstrated mild to moderate nausea and vomiting. Hepatic toxicity was mild to infrequent. Only four patients showed cardiac toxicity which was not life-threatening. The most troublesome toxicity was mucositis and was seen in 11 patients; four whom required I.V. hyperalimentation. We conclude that this combination is an effective salvage program for relapsed prior-remitting ANLL. Future studies should be conducted in three areas. The first study might be a comparison of relapsed prior-remitting ANLL with single-agent m-AMSA. The second, in untreated ANLL, following induction with DAT, might use m-AMSA-AZA in consolidation and maintenance arms of future protocols. The final study should explore m-AMSA-AZA activity in evolved CML in a greater number of patients.