Thirteen patients with acute nonlymphocytic leukemia underwent autologous bone marrow transplantation (ABMT) following high doses of cyclophosphamide and total body irradiation while in first complete remission. After marrow infusion four patients received human leukocyte interferon and nine received intravenous methotrexate. One patient died on day 16 of septicemia associated with severe gastrointestinal toxicity. In the remaining 12 patients the median day of achieving a circulating granulocyte level of 500/mm3 was 29 (range 15-94 days). Eight of 12 evaluable patients achieved a sustained platelet count of 20,000/mm3 or greater in a median of 44 days (range 12-116 days) and four patients did not achieve this level before death on days 116-396. One patient died on day 116 of interstitial pneumonitis secondary to cytomegalovirus. Eight patients relapsed 58-365 days after AMBT (median 335 days), and all have died. Three patients are alive and well without relapse 26-50 months after ABMT. This study demonstrated that poor engraftment was a frequent complication of ABMT when early posttransplant cytotoxic therapy was attempted. Relapse of leukemia and the number of long-term survivors in this small group of patients was not different from that expected following conventional therapy.