The influences of endogenous factors (sex, age, premorbid personality traits, heredity) and exogenous factors (somatogenias, cranial injuries and neuroinfections, intoxications, psychogenias) on the origin and course of psychotic syndromes and dementia were regarded on the basis of clinical and epidemiological studies carried out in 523 patients with cerebral atherosclerosis. The leading risk factors were established for each form of mental disorders due to cerebral atherosclerosis.