ABSTRACT.In a prospective longitudinal study of a cohort of 105 subjects born prematurely, competence was assessed from infancy through late adolescence. A biosocial model guided the research. Neohatal neurobehavioral organization (a composite of term visual attention, amount of time in active sleep, and 407 EEG pattern) and early social stimulation (the amount of talking the mother addressed to the infant during a home observation when the infant was 1 month old) in conjunction with social class were used to predict competence at key age periods through late adolescence. Intellectual competence, school achievement, social competence, and self perception of cognitive competence were studied. The results indicate that measures taken in the early infancy period were predictive of later competence, particularly intellectual competence, above and beyond social class. Twenty-eight percent of the variance in 48-year IQ scores was explained by the predictor variables. The study highlights the importance of directing efforts to improve the social environment of both the infant and the family.J Dev Behav Pediatr 16:36–41, 1995.Index terms:prematurity, competence, biosocial factors, late adolescence