AbstractHistorically, vinblastine given by intravenous bolus injection has not been an effective treatment for non-Hodgkin's lymphomas; vincristine has displayed greater activity. Also, vinblastine has generally been considered to be cross-resistant with vincristine in such patients. In an attempt to overcome these obstacles, a protracted infusion of vinblastine was administered (0.5–1.5 mg/m2per day for 5 days) and repeated every 3 weeks. Partial responses were observed in 4 of 29 (14%) patients with a variety of non-Hodgkin's lymphoma lasting 2.4, 2.4, 5.5, and 9.0 months. Just prior to treatment the responding patients had received and eventually become refractory to vincristine. These data show a lack of total cross-resistance between vinblastine and vincristine which might have important therapeutic implications in this disease.