To examine children's patterns of social interaction in group care, the activities and verbal behavior of 50 preschool children attending 5 Japanese day care centers in metropolitan Tokyo were observed and recorded during a total of 20 minutes of free play for each child. Participants were equally dispersed across five age categories each encompassing 6 months and collectively extending from 6 months to 3 years of age. Observations made in 10-minute blocks were recorded at 30-second intervals. Five mutually exclusive categories comprising a heirarchical ordering of involvement were used to code the data: "solitary,""watches,""parallel play,""interaction," and "interchange." Results indicated that, in the "watches" category, the youngest group had significantly higher scores than those in either of the two oldest groups. The frequency of "parallel play" among the youngest was significantly lower than for all other age groups. Children from 12 to 36 months of age were found to spend significantly more time engaged in parallel play than were infants under the age of 1 year. Children as young as 12- to 18-months-old were spending approximately one-fifth of their time in parallel play. It is concluded that, while this finding can be explained in part by developmental considerations, culture or environment appeared to be a contributing factor. (RH)