Small doses of vincristine sulfate produced dramatic improvement in patients with far-advanced reticulum cell sarcoma which previously had been resistant to other forms of therapy. The maximal initial dose was 25μg/kg body weight weekly; maintenance levels have been as low as 5μg/kg biweekly. This dosage schedule permitted prolonged courses of therapy and minimized toxicity, thus providing sustained antitumor effect. In one patient with disseminated reticulum cell sarcoma refractory to alkylating agents and irradiation, a 17-month course of therapy was tolerated without toxicity. Death, due to unrelated causes, occurred 29 months after initiation of vincristine; no tumor was found at autopsy. It is suggested that vincristine, given in small doses for weeks or months, is a systemic agent worthy of consideration for the primary therapy of generalized reticulum cell sarcoma.