Clinical trials of pentoxiphylline (trental) used in the treatment of 164 patients were carried out. Of these patients, 32 were suffering from acute cerebral circulation disorders, 25 from chronic cerebrovascular insufficiency, 50 from cerebrovascular dystonia of various genesis, 12 from peripheral vasculopathy, and 5 from migraine. A favourable effect of pentoxiphylline on the course of the cerebrovascular disorders (except migraine) was noted. Rheographic examinations confirmed the improvement of the cerebral and peripheral circulation and revealed a two-phase effect of the drug on the vascular tone that manifested in alternations of periods of short-time moderate vasodilatation and vasoconstriction. Pentoxiphylline was also found to produce a venotonic effect. The pharmacodynamic mechanisms of the hemovascular effects of the drug are discussed. The optimal dose of pentoxyìphylline for a single intravenous injection is assumed to be 10 ml of solution containing 200 mg of the drug dissolved in physiological saline. The optimal dose for drop infusion is up to 15--20 ml of the same solution. In addition the drug is to be given orally in a dose of 400 mg (two dragees of 200 mg) two or three times a day. The treatment lasts 3 to 5 weeks.