Effects of early experience and peer-group socialization on later play behavior of baboons (Papio sp) was assessed. The potential for development of sex differences in play behavior in the absence of sex-role models was of particular concern. Social play of nursery-reared baboons was contrasted with that of mother-reared conspecifics during late infancy (6–12 mo) and the late-juvenile period (36–42 mo). Males played more than did females and infants played more than did juveniles. There was no significant influence of early rearing conditions on play behavior despite effects on other behaviors. There were consistent sex differences in play behavior even for the individuals with no early access to sex-role models. This result is consistent with previous research indicating a strong hormonal basis of sex-differences in primate play behavior.