Spinal fluid from 53 HIV infected patients has been reviewed. A diagnosis was made exclusively from the spinal fluid exam in 15 cases while in 15 others it contributed to diagnosis together with other exams. The exam did not contribute any positive data in 23 cases. AIDS diagnosis was obtained in 11 patients by the spinal fluid exam. The most frequently occurring disease was infectious meningitis (10 cases) being 3 of them HIV aseptic meningitis. In our experience, a spinal fluid exam in HIV infected patients and fever of unknown origin did contribute useful data for the diagnosis of AIDS in a large number of cases.