This study sought to describe the norms of reciprocity in social interaction from the viewpoint of immediate behavioral exchanges by examining the social interaction of preschool peers in a free-play situation. Seventeen 4-year-old children, eight girls and nine boys, were observed during free play activity periods after a picture sociometric test had been administered. A coding system was used in recording different behavior transactions between individuals. The various code categories were verbal give, verbal receive, physical give, physical receive, verbal negative, verbal positive, physical negative, physical positive, do commands, don't commands, comply, and refuse. Sequential analysis was employed to examine the degree of reciprocity within particular interaction sequences. In this study analyses were concentrated only on the emotional affect categories (positive and negative patterns) without regard to their physical or verbal character. Furthermore, the unit of analysis was the occurrence of a particular type of behavior, not the activities of a specific individual. The findings revealed that reciprocal relationships were pervasive in preschool children's social interactions. A positive reciprocity norm was found in interactions among girls but not among boys. A negative reciprocity norm, however, was found for both sexes. In addition, it was found that the degree of reciprocity varied as a function of popularity. (Author/RH)