Markers for HIV-associated dementia (HAD) are needed for diagnosis and management. Specific antibodies to brain and immune complexes (IC) in the cerebrospinal fluid (CSF) are potential markers. CSF IC were found in 4 of 4 HAD patients, 2 of 2 AIDS-central nervous system (CNS) lymphoma patients with dementia, 0 of 1 AIDS-CNS lymphoma patient without dementia, 0 of 1 AIDS-CNS toxoplasmosis patient without dementia, and 0 of 10 neurologic disease controls. By blinded immunoblots, antibrain antibodies in serum and CSF were found in 11 of 12 HAD cases and 7 of 19 HIV-1 patients without HAD. All 11 non-HIV-1 controls were negative. These and published data suggest antibrain antibodies and IC may serve as markers of HAD.