Naturalistic observation of the spontaneous role-taking behavior of 16 four-year-old children (8 boys, 8 girls) in a free play situation with a same-sex peer was used to investigate the sex role perceptions and preferences of young children. Videotape recordings of the unelicited male, female, parental, and conjugal role portrayals were examined in terms of the children's perception of those roles along the competence and nurturance dimensions, as well as in terms of the tasks and general attitudes associated with the roles. It was found that in the parental role the female is viewed as highly competent; but in the conjugal role, (within which the role relation shifts from the child to the husband) her competence diminishes dramatically. The male, in contrast, appears the more competent in the conjugal role and the less competent in the parental role. The accuracy, depth, and breadth of the children's sex role portrayals is discussed, as well as the preference for same-sex role play. Also included is a discussion of the assimilative and accommodative functions of role play in the early acquisition of sex role and the degree of decentration required for the role play activities to occur. (Author/MS)