To assess the relationship between paternal behavior and the intellectual functioning of preschool boys and girls, 180 white fathers from middle, working, and lower classes (as defined by the Hollingshead-Redlich Scale) were observed at home interacting with their 4-year-olds (99 boys and 81 girls). Sessions were tape-recorded. The number of father behaviors occurring in a 30-minute period were computed according to 25 pre-selected categories. The children were subsequently tested on the Stanford-Binet Intelligence Scale and on a set of standardized Piagetian tasks to assess their intellectual competence. Factor analysis of the 25 categories of father behaviors yielded 4 factors for father/son interactions and 6 factors for father/daughter interactions. Significant differences were found in the relationship between the behaviors of fathers in different social classes and the measures of their sons' cognitive functioning; but no such significant correlations were found between father behaviors and daughters' cognitive measures (although father's occupation became a significant predictor variable). Findings were discussed in terms of the child's sex role identification, and the observed differences in the behaviors fathers exhibited towards sons and daughters. (ED)