A phase I study of a new cisplatin derivative for hematologic malignancies. DWA2114R (DWA) is a new derivative of platin compounds that is currently being used in Phase II studies of solid tumors in Japan. The dose-limiting factor is myelotoxicity with mild extramedullary toxicity. This Phase I study consisted of adult patients with relapsed hematologic malignancies. Eight patients received a total of 15 treatment courses of DWA. The starting dose was 800 mg/m2 over 24 hours by continuous infusion. The dose was first increased to 1200 mg/m2 and then to 1600 mg/m2. Clinical toxicity and urinary excretion studies of DWA suggested that 1200 mg/m2/d for successive days would be the best type of administration. When 1200 mg/m2/d was given for 5 days, Grade 2 to 3 diarrhea and nausea and vomiting were encountered requiring parenteral fluids and nutritional support. This suggested that the dose-limiting factor with this schedule was gastrointestinal toxicity. Myelotoxicity was severe, as expected, but tolerable. One of the five patients with acute nonlymphocytic leukemia (ANLL) entered into complete remission and one patient with chronic myelogenous leukemia (CML) in crisis returned to the chronic phase. A Phase II trial of DWA is warranted for hematologic malignancies, especially in myeloid diseases. 