Extrapulmonary involvement with Pneumocystis carinii has been described in 0.5%-2.5% of persons with AIDS. One hundred nine patients with AIDS and confirmed extrapulmonary pneumocystosis were identified, and seven of these patients (including our patients) had central nervous system (CNS) pneumocystosis. Of these seven patients, six had prior AIDS-related complications, and three had previous P. carinii pneumonia. Six patients had CNS symptoms, one of whom underwent a focal neurological examination. No cases were diagnosed before death. The involved sites were the cerebral cortex (2 patients), meninges (2), pituitary gland (1), putamen (1), and nonspecified locations (3). In two patients, organisms were seen around blood vessels, and in five patients there was concurrent neuropathology. In summary, CNS involvement with P. carinii usually occurs as a late complication of AIDS and probably represents hematogenous dissemination.