Peer-peer interaction among 10–21- and 24–30-month-olds with extensive daycare experience was studied. Thirteen pairs of familiar agemates were formed, and each dyad was observed in a playpen with toys at their daycare center. Adult preparation and various constraints to peer-peer interaction were minimized. The nine behavioral measures included nonsocial, marginally social, and social play categories. The results revealed equivalent amounts of nonsocial behavior for both age groups, and marginally social behavior was not the dominant play activity at either age. Compared with the younger group, the older children engaged in less marginally social activity, more positive social behavior overall, and more sustained sociable interchanges. Neither age group had high levels of antisocial behavior, but the younger children tended to display more than the older. Support was found for the view that marginally social activity functions as a bridge from nonsocial to social behavior.