Preleukemic syndromes are a group of acquired bone-marrow disorders characterized by dysplastic maturation of hematopoietic cells and peripheral-blood cytopenias. Although the clinical course is variable, most patients succumb to hemorrhage, infection, or acute leukemia. These syndromes are generally considered untreatable. We administered low doses of cytarabine by continuous intravenous infusion for 7 to 21 days in eight patients with preleukemia or with preleukemia in evolution to acute leukemia. Eight of 13 courses were associated with marked increases in peripheral-blood granulocyte, platelet, and red-cell counts, with the result that six of the eight patients needed no transfusions for 2 to over 14 months. These preliminary results demonstrate that continuous infusion of low-dose cytarabine can offer patients with preleukemic syndromes hematologic improvement with limited toxicity.