At the age of 29, a woman developed central nervous system manifestations of incontinence, psychosis and a grand mal seizure in February 1982. She was diagnosed as having systemic lupus erythematosus (SLE) based on photosensitivity, oral ulcers and elevated antinuclear and anti-DNA antibodies titers. Three years and one month later the patient had episodes of severe headache and vomiting during the course of maintenance treatment. CT examination of the head revealed blood within subarachnoid cisterns, and a small berry aneurysm was found at the distal portion of the basilar artery by cerebral angiography. The possible role of SLE-associated cerebral vascular changes in the development of this aneurysm is discussed.