The authors describe a modification of the encephalo-duro-arterio-synangiosis (EDAS) surgical technique for patients with moyamoya syndrome in which the arachnoid is widely opened over the exposed brain and the donor superficial temporal artery adventitia is sutured directly to the pia with 10-O nylon suture ('pial synangiosis'). The procedure has been performed in 34 patients over a 10-year period, with follow-up arteriograms 1 year following the procedure demonstrating markedly enhanced middle cerebral artery flow through the surgical site. Operative morbidity has been limited to two postoperative strokes, both in patients who were neurologically unstable preoperatively; and the clinical stability of the operated patients has thus far been excellent.