Social participation behavior of 33 2- and 3-year-old children was observed during free-play in order to identify differences between age groups as well as differences between contemporary outcomes and Parten's 1932 findings. Trained observers recorded the frequencies of play behaviors, utilizing a time sampling procedure and Parten's categories of social participation: unoccupied, onlooker, solitary, parallel, associative, and cooperative. Data were gathered on family size, birth order, and children's additional group experiences. Participating boys and girls were enrolled in four church-sponsored mother's-day-out or nursery school classes. Each child was observed at least 20 times for 1 minute by several observers. Findings indicate that 2-year-old and 3-year-old children engaged in solitary and parallel play more than half the time. The 3-year-old subjects engaged in significantly more associative and cooperative play than did 2-year-olds. Play behavior differed significantly by sex in both age groups. Parten's sample exhibited more social types of play than did the children in the present study. While 2-year-olds showed no pattern of choosing play partners by sex, 3-year-old girls tended to choose girls for cooperative play. Differences on some variables across observation rounds were evident, but no clear relationship between family and group factors and the six types of social participation was found. Implications for research and classroom practice are pointed out. Appendices consist of: letters to parents; observers' training and experience; a coding sheet; and the observation schedule. (RH)