An analysis of 1999 courses of psychopharmacotherapy (PPT) conducted in 90 patients with attack-like forms of schizophrenia and in 122 patients with the paranoid form has revealed an adverse effect of cerebro-organic insufficiency on PPT tolerance. In patients with the maximal degree of residual cerebro-organic insufficiency an elevated sensitivity to PPT occurred 2-2.2 times as often as in patients with a history of the minimal number of exogenously aggravated factors. PPT tolerance depended on both the nature of diseases and the age when they occurred. To evaluate the nature of pathogenic effect on the brain, all aggravating factors were divided into evidently cerebral, conditionally cerebral and other than cerebral ones. The highest intolerance was observed when evidently and conditionally cerebral aggravating factors were combined and when their combined development occurred in both early and late periods of ontogenesis.