To compare the value of ABMT (allogeneic bone marrow transplantation) in first or second remission vs. conventional chemotherapy in adults with acute nonlymphocytic leukemia, we examined retrospectively the outcome of a recently completed chemotherapy trial. We evaluated the survival of patients, with and without histocompatible siblings, who were less than or equal to 45 years old and who had achieved initial complete remission. Of 20 patients who were referred by their physicians for ABMT in first remission, seven relapsed (median duration of remission, 4 months) prior to ABMT, three refused, and 10 underwent ABMT. Nine patients received ABMT in second remission. In comparison to the results of chemotherapy in patients who lacked histocompatible siblings (median duration of survival, 18.5 months), the survival of patients transplanted in first remission was worse (median, 8 months), whereas the survival of patients transplanted in second remission was substantially better (median greater than 22 months). Although ABMT in second remission clearly offers the potential for long-term survival not available by means of conventional chemotherapy, the value of ABMT in first remission remains uncertain.