Twenty-one patients with hematopoietic malignancies including 6 previously untreated, 9 pretreated, and in relapse, 5 in complete remission and one in partial remission all were treated with PL-AC. The patients consisted of 12 acute myelocytic leukemias, 4 acute monocytic leukemias, 2 acute lymphocytic leukemias, one erythroleukemia, one malignant lymphoma and one chronic monocytic leukemia. PL-AC was given orally at a dosage of 50-1200 mg daily. Mean total dosage was 4.74 g (0.6-15.25), and the mean administration period was 3.43 days (1-122). days Responses were observed in 4 out of 9 pretreated patients by a decrease of blast cells in the peripheral blood. Partial remission was obtained in one case which lasted 8 months. Out of 5 previously untreated acute leukemias, one partial remission and 4 hematological responses were observed. The plasma concentration of Ara-C was maximal at 3 hours and was not detectable after 12 hours. Side effects observed were nausea in 5 patients vomiting in one patient and liver dysfunction in one patient. These side effects however were not so severe as to stop drug administration. PL-AC may be administered in doses ranged 150-250 mg for 2-3 weeks without any severe side effects, and with some clinical effects.