Visual evoked potentials versus flash (VEP) and brain DC-potentials were studied in the first-order relatives of patients (mean age 42.6 +/- 1.6 years) with Alzheimer's disease (AD) and probands (mean age 60.9 +/- 0.9 years) and age-matched healthy controls for the relatives and probands. In the relatives of AD patients, the latencies of N2, P3, N3 components were found to be delayed as compared with the controls. There was a delay in the latencies of the same components in the patients and their relatives, but it was smaller in the relatives of AD patients. The brain DC-potentials were higher in the relatives of AD patients than in the controls. Neurophysiological changes in the relatives of AD patients may be considered to be signs of latent neurodegeneration in the limbicoreticulocortical pathways, which may be associated with the excitotoxic processes and abnormal hyperactivity in the limbicoreticulocortical structures.