In 1982 we began a prospective controlled trial to assess the effectiveness of allogeneic bone marrow transplantation and intensive post-remission chemotherapy for patients with acute myelogenous leukaemia in first complete remission. Fourteen patients, 3-45 years of age, who had an HLA-identical sibling donor, received bone marrow transplantation. Twenty-five patients who either lacked an HLA-identical sibling or were over 45 years of age received intensive consolidation chemotherapy including high-dose cytosine arabinoside with or without adriamycin. The actuarial rate of continued complete remission (CCR) at 3 years was significantly higher in the transplantation group than in the chemotherapy group: 70% (95% confidence interval 35-91%) compared with 10% (95% confidence interval 2-30%); P = 0.01. However, the actuarial rate of CCR was not significantly different between the transplantation group and patients under 45 years in the chemotherapy group: 70% (95% confidence interval 35-91%) compared with 17% (95% confidence interval 4-45%), 0.1 greater than P greater than 0.05. The actuarial probability of leukaemia relapse was significantly lower in the transplantation group than in the chemotherapy group: 10% (95% confidence interval 4-21%) compared with 88% (95% confidence interval 70-96%), 0.005 greater than P greater than 0.001. There was no significant difference between both groups if we compare only the patients who died of non-leukaemic causes: 22% (95% confidence interval 9-42%) versus 25% (95% confidence interval 7-59%), P = NS. In summary, this study shows that allogeneic bone marrow transplantation is a better anti-leukaemic treatment than is intensive consolidation chemotherapy in patients with AML in first complete remission.