We report a case of right middle cerebral artery occlusion associated with ipsilateral basal moyamoya like vessels and ruptured anterior cerebral artery aneurysm. A 59-year old man suddenly developed a consciousness disturbance and was brought to our hospital by ambulance. On admission, computed tomography (CT) of the head revealed a diffuse dense high-density lesion in the basal cistern and in the bilateral sylvian fissures, and a round homogeneous high-density area in the interhemispheric fissure. Subsequent angiography showed a large anterior cerebral artery aneurysm and occlusion of the right middle cerebral artery with moyamoya-like vessels. We made a diagnosis of subarachnoid hemorrhage due to aneurysm rupture. An emergency bifrontal free bone craniotomy was performed, utilizing the interhemispheric approach and the neck of the aneurysm was clipped. On the 68th postoperative day the patient was ambulatory and discharged from the hospital. Hemodynamic stress was thought to be the main cause of the anterior cerebral artery aneurysm. Because the laboratory data on admission included a false-positive serological test for syphilis, we tested the patient for antiphospholipid antibodies, and repeatedly found anticardiolipin antibody in the patient's serum. The antiphospholipid antibody syndrome may have been responsible for the occlusion of the middle cerebral artery, in this patient and we think that testing for serum antiphospholipid antibodies is important in occlusive cerebral artery disease, especially in moyamoya disease or when moyamoya-like vessels are present.