Twenty-seven patients aged from 10 to 60 years (mean 34.4 +/- 13 years) in the first perceptible phase of acute myeloid leukemia were subjected to intensive induction chemotherapy consisting of adriamycin (ADM), vincristin (VCR) and cytosine arabinoside (ARA-C). Twenty-four patients (89%) attained complete remission (CR) after 1 to 3 cycles and were then given an early consolidation treatment with one of the previous cycles. This was followed by long-term continuous maintenance chemotherapy with 6-mercaptopurine (6-MP) and methotrexate (MTX) alternatively and 3-monthly reinforcement courses of donaurubicin (DNR) and VCR. Twenty of these 24 patients were splenectomized soon after the consolidation treatment. None of the spleens were enlarged, and histological sections of the spleens, liver biopsies and mesenteric lymph-nodes stained with routine dyes and by the naphthol AS-D chloroacetate esterase method revealed mature granulocytes but no demonstrable leukaemic cells. In the group of splenectomized patients, the probabilities of staying in complete remission at 27 and 44 months were 70 +/- 12.6% and 52 +/- 18.5% respectively, and the probabilities of remaining alive at 32 and 55 months were 79 +/- 11% and 57 +/- 19% respectively. Age over 40 and evidence of extramedullary infiltration at presentation appeared to leave little hope of disease-free survival. The rationale for the present therapeutic study is discussed.