Vindesine, a semisynthetic derivative of vinblastine sulfate, was tested for antitumor activity and clinical toxicity in 36 children. The drug was administered to the initial 13 patients entered into the study a 2 mg/m2/day for five days by IV bolus. Because of severe neurotoxicity and life-threatening gastrointestinal toxicity, the regimen in 23 patients was modified to 4mg/m2 IV infusion over four hours, weekly. This latter regimen was well tolerated, with acceptable gastrointestinal, hematological, and neurotoxicity. One child with acute lymphocytic leukemia resistant to vincristine had a transient M1 remission bone marrow. Improvement or stable disease was noted in one patient each with Ewing's sarcoma, neuroblastoma, and Hodgkin's disease.