Extra-intracranial by-pass between a branch of the external carotid artery and a branch of middle cerebral artery has been used since 1972 in the treatment of cerebral ischemia. METHODS 40 patients have been operated on (34 men and 6 women) aged from 28 to 68. Clinical data were TIA's or PRIND in 11 patients and stroke in 29 patients. The left hemisphere was involved in 25 cases and the right one in 15 cases. No patient was operated on in emergency; operation was performed after 2 or 3 weeks in most cases. The branch of external carotid artery was the superficial temporal artery in 36 patients and the occipital artery in 4 patients. As for the cerebral artery, were used the anterior temporal artery (9), the middle temporal artery (2), the posterior temporal artery (15), the angular artery (6), a frontal artery (15) and a parietal artery (1). In 8 patients, two anastomosis were performed using both branches of STA. Patency of the by-pass was confirmed in most cases by means of angiography, performed early after operation, and if possible one year later.