Twenty patients treated with maintenance chemotherapy for acute nonlymphoblastic leukemia after achieving complete remission were compared with 13 patients who underwent bone marrow transplantation from an HLA-identical sibling. The median age was 27 years for both maintenance chemotherapy patients (range 17-42 years) and for patients undergoing bone marrow transplantation (range 16-42 years). The 1-year survival for maintenance chemotherapy was 80% vs. 54% with bone marrow transplantation (p = NS). Complete remission durability was 70% at 1 year for maintenance chemotherapy (34% projected for 5 years) compared with no relapses in the first year with bone marrow transplantation (p = 0.01). Patients on maintenance chemotherapy were hospitalized for an average of 22 days (range 0-171 days) during the first 12 months of treatment. Patients undergoing bone marrow transplantation were hospitalized for an average of 82 days (range 41-113 days) in the same time period. Severe hematologic toxicity was seen in 13/13 bone marrow transplantation patients and 6/20 maintenance chemotherapy patients. Chronic graft-vs.-host disease occurred in 3/7 surviving bone marrow transplantation patients. Maintenance chemotherapy had an average first year cost of +3,076.00 for patients who did not relapse and +48,827.00 for patients that relapsed. The first year costs for bone marrow transplantation averaged +84,102.00. Thus, maintenance chemotherapy was associated with a better early survival, less toxicity, and lower cost than bone marrow transplantation in the first year after initiating therapy. However, fewer relapses with bone marrow transplantation suggest that it will yield a higher long-term survival rate.