«Intermediate phenotype» (endophenotype) is an important term when studying the mechanisms which are involved in the genotype's influence on the psychometric intelligence. It has been demonstrated that parameters of evoked potentials (EP) as correlates of functioning of brain systems involved into visual information processing may serve as intermediate phenotypes of intelligence. Analysis of genetic correlations indicates the special role of parameters of the EP of the frontal lobes during semantic information perception. Parameters of the EP in primary school age and adolescence may be used for prediction of intelligence in maturity. The effectiveness of prognosis reveals the dependence on a parameter of the EP, type of a stimulus, registration area and subjects' age. The presence of genetic correlations between EP parameters and intelligence indices proves the existence of joint genetic factors included in formation of interage inter-level phenotypic connections between different indices of individual's cognitive functions.