In Study 1, eight- and 11-year-old children's participation in playground activities was examined by means of direct observations. At both ages, the two most common categories of behaviour engaged in were sociable activities and rule games. The older children spent significantly more time in rule games and significantly less time alone than the younger children. Girls spent significantly more time in sociable activities and significantly less time alone than boys. The proportion of time spent in these and other categories of behaviour was not found to differ from the beginning to the end of playtime. A more detailed analysis revealed the proportion of time spent in some more specific games and activities, as well as other age and sex differences. Many activities were found to be typically single sex and/or single age affairs, although others were more often played in mixed sex and/or mixed age groups. Some of the reasons for why this was the case were explored in Study 2, along with the children's feelings at being excluded by other groups. It appeared that the older boys were largely responsible for the lack of mixed age and mixed sex play on the playground.