This report presents studies of the neurophysiological correlates of the characteristics of cognitive disorders in patients with first psychotic episodes of endogenous psychosis at juvenile age. Three groups of patients were studied: those with a predominance of catatonic symptomatology (22 patients), those with a predominance of hallucinatory-delusional symptomatology (22 patients), and those with a predominance of affective-delusional symptomatology (24 patients), along with a group of psychologically healthy subjects (15 subjects). Parameters of auditory evoked potentials were analyzed using the oddball paradigm. The group with a predominance of catatonic disorders showed the greatest differences in the latent periods (LP) of the N200 and P300 components as compared with the other groups; patients with a predominance of hallucinatory-delusional symptomatology showed the most localized anomalies in the latent period of the P300 component; the group of patients dominated by affective-delusional symptomatology showed almost no increase in the latent period of the N200 component, though the extents of anomalies in the N100 component in responses to non-target signals and deviations in the P300 component were more marked than in the other groups. These characteristics of the neurophysiological correlates of cognitive functions in each group of patients supported the significance of evaluating the psychopathological structure of manifest psychotic episodes for determining the clinical typology.