A report on the EC/IC bypass study.

In 1967 the first extracranial to intracranial (EC/IC) arterial anastomosis was performed. Since that time, EC/IC bypass surgery has become a widely accepted surgical treatment for patients with intracranial stenotic or occlusive atherosclerotic lesions. In 1977 an international multicenter randomized trial was established to determine whether EC/IC bypass surgery reduced the rate of stroke and stroke-related death in patients with recent hemispheric and/or retinal ischemic symptoms. Completed and analyzed in 1985, the International Cooperative Study of Extracranial/Intracranial Arterial Anastomosis of 1,377 patients provides an evaluation of the surgical procedure for stroke prevention. This paper will discuss the study's objectives and organization, the methods employed, the trial results, and implications.