The relationship among different settings for young children's play behaviors and peer interactions was examined. The participants were forty-one children from 2 to 5 years of age (21 2- and 3-year-olds and 20 4- and 5-year-olds) enrolled in three child care programs. The children were videotaped for 5 minutes each on 4 different days both indoors and outdoors. Program measures described the quality of the child care program (the Assessment Profile for Early Childhood Programs) and additional measures described the playground setting. Children's play behaviors were categorized using the Parten-Smilansky Scale, which combines social play categories and cognitive play categories (Rubin, Watson, & Jambor, 1978) using 16 categories of play behavior. Children's peer interactions were categorized using the Peer Play Scale (Howes & Matheson, 1992). Results indicated that all six classrooms and their related playgrounds were mediocre child care programs. Children were more likely to engage in parallel functional play and the highest form of peer play (i.e., social pretend play) and play behavior (i.e., interactive dramatic play) outdoors than indoors. The younger age group was more likely to be engaged in playing alone or interacting with adults, whereas the older age group was more likely to interact with peers. These findings reinforce the importance of both the indoor and the outdoor environment for promoting more complementary play behaviors and peer interactions. Finally, additional findings of relationships between the Parten-Smilansky Scale and the Peer Play Scale showed that the combination of the two scales provide a more valid and comprehensive assessment of children's social interactions with peers in naturally occurring contexts.