A phase II evaluation of vindesine (VDS) was carried out in 46 patients with hematologic malignancies refractory to conventional chemotherapy. Two VDS schedules were employed (at random): (A) a weekly bolus (5 mg/m2 i.v. X 4); (B) fractionated daily injections (0.5 mg/m2 i.v. q.12 h X 10, course to be repeated after 10-15 days). Complete and partial remissions were observed in acute lymphocytic leukemia (3/14 patients), acute non-lymphocytic leukemia (2/12 patients), chronic myelocytic leukemia in blastic crisis (4/12 patients) and non-Hodgkin's lymphoma (4/8 patients). Responses were seen with higher frequency in patients treated with the weekly bolus (42.8 vs 16%). Myelosuppression was the most relevant side effect in both schedules. Neurotoxicity occurred infrequently and was generally mild in degree. Further trials with VDS in combination with other drugs are recommended in hematologic malignancies.