We evaluated the role of ABMT in late 1st CR AML adult patients using busulfan plus cyclophosphamide as preparative regimen. Fifty-one adult patients (mean age 36 years, range 15-59) with AML underwent ABMT in 1st CR. Three of them had a prior diagnosis of myelodysplastic syndrome; one patient had a secondary leukemia. The median interval between CR and ABMT was 8 months (range 4-20). Patients received busulfan, 4 mg/kg/day for 4 days plus cyclophosphamide 50 mg/kg/day for 4 days or 60 mg/kg/day for 2 days. No maintenance chemotherapy was administered after ABMT. Median days to reach 0.5 x 10(9)/I PMN and 20 x 10(9)/I platelets were 26 (range 12-250) and 74 (range 16-740), respectively. No transplant-related deaths were observed. Five-year actuarial overall survival rate is 76.9%; actuarial leukemia-free survival rate is 70.6%. Mean follow-up from ABMT is 35 months. Leukemia-free survival of this group was compared with that of 38 non-transplanted patients younger than 60 years, who maintained a CR longer than 8 months in the same period. This analysis shows a statistically significant difference in favor of ABMT patients. These results suggest that, even if performed late after 1st CR as post-remission intensification, ABMT can improve the outcome of AML patients.