The natural history of MCA occlusion has become increasingly important since the surgical option of EC/IC bypass surgery has been available. The clinical course of 24 patients with angiographically-demonstrated occlusion of the MCA artery was reviewed. Eight patients presented with a major disabling stroke and five of these died during the acute phase of this ischemic event. The remaining 19 patients were followed for a mean of 54.2 months. There were five deaths in follow-up and two of these were due to subsequent strokes. Fourteen patients manifested a benign course: one of these had a further minor stroke and four had TIAs. Altogether, 3 strokes occurred during the follow-up period (2 fatal, 1 minor) and all were in the territory of the artery known to be occluded. Of those patients who survived their presenting ischemic event, 12 (63%) remained completely functional in terms of activities of daily living. MCA occlusion does not necessarily carry a poor prognosis with medial therapy alone and the role of bypass surgery hopefully will be clarified by the ongoing clinically randomized trial.