A complete remission of 5-16 months' duration was achieved in 5 of 6 consecutive patients with acute promyelocytic leukemia treated with Daunomycin and platelet transfusions. Although 4 patients had coagulation findings suggesting disseminated intravascular coagulation, heparin was given in only one case. Heparin infusion was twice accompanied by normalization of the fibrinogen level, but had to be stopped because of severe bleeding. In the other 5 patients chemotherapy was not accompanied by increased bleeding, although 1 patient showed an initial worsening of the coagulation findings. Platelet substitution and intensive chemotherapy appear to play a more crucial role than theoretically questionalbe treatment of the plasmatic coagulation disturbance. 2 patients had central nervous system involvement, a complication previously thought to be extremely rare in acute promyelocytic leukemia.