The frequency of neurological manifestations was evaluated in 653 HIV infected patients admitted in a university hospital in Rio de Janeiro city, Brazil, in the 1985-1989 period. A total of 172 (26%) patients developed neurological symptoms. Central nervous system complications included: cerebral toxoplasmosis (80), cryptococcal meningitis (57), subacute encephalitis (17), tuberculosis (8) and aseptic meningitis (2), progressive multifocal leukoencephalopathy (2) and vacuolar mielopathy (6). Peripheral neuropathy occurred in three cases. The clinical and tomographic aspects were analysed. The majority of the patients died within six months after the onset of the neurological disease.