Because little was known about the prevalence of neurological complications of human immunodeficiency virus type 1 (HIV-1) infection in Africa, we conducted a cross-sectional study among consecutive admissions to the internal medicine wards of Mama Yemo Hospital in Kinshasa, Zaire. Of the 196 patients studied, 104 (53%) were HIV-1 seropositive, of whom 50 (48%) had stage 3 and 49 (47%) had stage 4 HIV-1 infection according to the provisional WHO staging criteria for HIV infection. Neuropsychiatric abnormalities were present in 43 (41%) of 104 HIV-1-seropositive patients. Of the HIV-1-seropositive patients, 9 (8.7%; 95% confidence interval, 4-16%) were diagnosed as having possible HIV-1-associated dementia complex, 1 (1%) as having possible HIV-1 myelopathy, and 3 (2.7%) as having possible HIV-1-associated minor cognitive/motor disorder. Definitive diagnoses could not be made because there were no facilities for neuroimaging and neuropathology. Meningitis caused by cryptococcus was diagnosed in six (5.6%) and by Mycobacterium avium in two (2%) of the HIV-1 seropositive patients. Acute onset hemiplegia, believed to be due to stroke, was present in four (4%) of the HIV-1-seropositive patients. The prevalence of other central nervous system opportunistic infections and mass lesions, especially toxoplasmic encephalitis, could not be assessed. In this population of Zairian inpatients, the prevalence of neurological complications of HIV-1 infection was similar to that observed in industrialized countries among patients with advanced HIV disease.