Fifty-nine children, aged 1-15 years, with acute myelogenous leukemia (AML) received a bone marrow transplant (BMT) from an HLA-identical sibling (n = 57) or from an identical twin (n = 2), while in first remission (CR). These children represent, to the best of our knowledge, all children grafted in first CR in 11 Italian centers between 1980 and 1990. Patients were prepared with total body irradiation (TBI) plus cyclophosphamide (CY) (n = 50) or melphalan (n = 2) or with busulfan plus CY (n = 7). GVHD prophylaxis consisted of cyclosporin A (n = 48), methotrexate (n = 7) or cyclosporin and methotrexate (n = 2). Survivors have been followed for 21-137 months (median 59 months). Actuarial relapse-free survival was 58% at 66-137 months (95% confidence interval (CI) 44-72). Actuarial risk of relapse was 23% at 48 months (95% CI 10.9-34.8). Risk of non-relapse deaths was 33% in the period 1980-87 and 4% in the period 1988-90 (p = 0.02). In multivariate analysis patients with a blood cell count > 14 x 10(9)/l at diagnosis showed a lower relapse-free survival compared with patients with counts < 14 x 10(9)/l (p = 0.006). We could not detect an effect of FAB subtype, patient age, time to achieve remission or transplant-related variables, including year of BMT, on relapse-free survival. In conclusion, allogeneic marrow transplantation can achieve long-term relapse-free survival in over 50% of children with AML and should be considered as consolidation therapy if a matched sibling is available.(ABSTRACT TRUNCATED AT 250 WORDS)