The European Stroke Prevention Study was a multicenter study comparing the effect of the combination of dipyridamole, 75 mg, and acetylsalicylic acid, 330 mg, three times a day, to that of placebo in 2,500 patients in the secondary prevention of stroke or death after one or more transient ischemic attacks, reversible ischemic neurological deficits, or strokes of atherothrombotic origin. The patients with vertebrobasilar events at entry comprised one-third of the whole patient population. The overall total incidence of stroke or death (the end points) during the 2-year follow-up in the placebo group was lower in the vertebrobasilar group compared to the carotid group (14% versus 24%, respectively). The combination therapy of dipyridamole and acetylsalicylic acid caused a marked reduction in the incidence of stroke or death in patients with vertebrobasilar (51%) and carotid (30%) events. When only stroke was considered as the end point, dipyridamole and acetylsalicylic acid seemed to be more effective in reducing the risk of transient ischemic attacks than stroke, and more effective in men than in women.