Three patients with idiopathic sideroblastic anemia of variable duration developed acute leukemia. In two the leukemia was morphologically and histochemically myeloblastic, in one lymphoblastic. With combination chemotherapy remission was achieved in all three. The remission inductions were complicated by long periods of bone marrow suppression and the duration of remissions was brief (3, 2 and 3 months). Survival after diagnosis was 13, 10 and 9 mo, respectively. The ring sideroblast abnormality persisted during the leukemic and remission phases and transfusion requirements remained unaltered in the two patients with transfusion dependent anemia throughout their courses.