Naftidrofuryl is a specific 5-HT2 receptor antagonist used since 1968 as a cardiovascular agent. Studies of rat spinal ganglion cultures have established that naftidrofuryl has effects on nerve growth. This study was conducted to evaluate naftidrofuryl for the prevention of peripheral neuropathy induced by vincristine sulfate. The study included 29 patients with lymphoid malignancies treated by combination chemotherapy including intravenous vincristine in a mean dose of 10.98 mg. Thirteen patients were randomized to oral naftidrofuryl in a dose of 600 mg/d and 16 were randomized to a placebo. Both treatments were given from the first day of the chemotherapy course to the eighth day after the end of the chemotherapy course. Double-blind evaluation of clinical and electrophysiological criteria showed that the only significant differences were decreased in the number and severity of polyneuropathies in naftidrofuryl patients as compared with control group. These data require confirmation by further clinical studies in humans.