Cerebral vascular insufficiency due to occlusive lesions regarded as inaccessible is a common problem. The degree of cerebral dysfunction associated with such lesions is dependent in part on the amount of collateral circulation present. By anastomosing the superficial temporal artery to a branch of the middle cerebral artery an increase in collateral circulation is provided to the affected hemisphere. This report describes the results of twenty such procedures. Postoperative angiography demonstrates a 90% patency rate. There is frequent neurological improvement following surgery, and the rate of new TIA's or strokes seems less than would be expected. The most damaging complication of the procedure ist intracerebral haemorrhage. The indications for, and the complications of, such procedures are discussed.