We examined 11 brains of human immunodeficiency virus (HIV) seropositive cases who died from unnatural causes (10 intravenous drug abusers who died from heroin overdose and 1 homosexual dead from a gunshot injury); 10 brains of HIV seronegative heroin addicts who died from overdose and 1 seronegative drug abuser who died from gunshot injury served as controls. Complete postmortem examination did not show evidence of acquired immune deficiency syndrome (AIDS) or AIDS related complex. Terminal changes including nerve cell ischemia, edema and diffuse vascular congestion were observed in all cases. Perivascular pigment deposition with macrophages was a constant finding in drug addicts and was probably related to chronic intravenous injection. In contrast, cerebral vasculitis was significantly more frequent and marked in HIV seropositive cases and was often associated with lymphocytic meningitis. Granular ependymitis, myelin pallor with reactive astrocytosis and microglial proliferation were also more frequent and more severe in HIV seropositive cases. Immunocytochemistry was negative for HIV antigens. Our study further supports the view that early central nervous system changes occur in HIV infection.