Flunarizine, a long-acting calcium antagonist, was studied in patients with peripheral vascular disease in order to assess its effects on blood viscosity, erythrocyte deformability, platelet activity and some clinical parameters. A randomized double-blind study was performed; all patients were given a standard diet, invited to abstain from smoking and to carry out a regular daily exercise (walking). After a 2-month run-in period the patients were divided into two groups: one was treated with flunarizine 10 mg/day and the other with placebo. The group treated with flunarizine presented marked and significant reduction of erythrocyte filtration time and blood viscosity and an improvement of the treadmill-free interval with a correlation between the parameters considered