Cognitive event-related potentials (ERP) were recorded in 100 HIV-positive patients of all CDC stages without clinical CNS deficits with an auditory oddball paradigm. Four latency peaks and three amplitudes were evaluated (N1, P2, N2 and P3 latencies, N1-P2, P2-N2 and N2-P3 amplitudes). In contrast to an age-matched control group of comparable education and social environment, a statistically significant N2-P3 amplitude reduction was found in the patient group deteriorating with the CDC stages. The physiological N2-P3 amplitude reduction with age in normals was found to be twice as fast in HIV-positive individuals. No group-statistically relevant EEG abnormalities were found in the patient group. In psychometric testing, there was no marked depressive syndrome in the HIV-positive individuals, but a mild slowing of speed-dependent abilities.