We examined 7-month-old infants' responses to 6 joy-eliciting episodes. Three episodes included and 3 did not include a major social-interactive component. Confirmatory factor analysis of infants' joy reactions in these episodes revealed that a 2-factor model significantly improved the fit over a single-factor solution. Those 2 factors represented infants' social versus nonsocial joy reactions. Different correlates of those factors supported their external validity. Only social joy was associated with the infants' positive emotional tone observed during naturalistic interactions with their mothers and fathers, and with the parents' ratings of the child's positive affect during social interactions in their daily lives. Social joy may be an early antecedent of future positive emotionality traits related to communal and interpersonal aspects of experience. (Contains 4 tables, 3 footnotes and 1 figure.)