The surgical management of adult moyamoya disease was evaluated retrospectively. Eight of 10 patients with hemorrhagic stroke had no bleeding episodes and eight of 11 patients with ischemic stroke were asymptomatic postoperatively. Angiography demonstrated neovascularization via the external carotid artery (ECA) in 22 sites (88%) and reduced basal moyamoya vessels in 11 sites (44%) postoperatively. These symptomatic improvements and angiographic findings suggest that reconstructive surgery for adult moyamoya disease patients with hemorrhagic or ischemic stroke is effective in decreasing hemodynamic stress in the basal moyamoya vessels and increasing the cortical blood supply via the ECA.