ONE OF THE most important advances in clinical cancer chemotherapy in recent years has been the demonstration that products of the periwinkle plant Vinca rosea Linn. have antitumor activity in patients with neoplastic disease.1 Vinblastine has been effective in patients with Hodgkin's disease and lymphosarcoma.2,3 There is also evidence for some degree of antitumor activity in a variety of solid tumors, particularly carcinoma of the breast, but the extent of this effect is not clear.1 The Eastern Cooperative Group in Solid Tumor Chemotherapy undertook preliminary studies of vinblastine in 1961. Dose response studies indicated that for the majority of patients 0.3 mg/kg was well tolerated, producing in most of the patients mild to moderate, reversible myelosuppression.3 Because occasionally a patient had myelosuppression with smaller doses, it was proposed that the doses employed in the therapeutic trial start at 0.1 mg/kg/week and be increased by 0.1 mg/kg/week to a maximum of