Subjects were 1,659 delinquents of 640 co-offending groups. This report presents data on the characteristics of companionship by using primarily the delinquents' responses to a questionnaire. Findings show that group members most often spent time at their own houses or a peer's house. Other places where groups gathered in order of frequency were school, parks, and streets or open places. As for the way they often spent time, talking ranked first, followed by playing computer games and loitering in the town. Members of shoplifting groups did not often spend more time loitering in stores than the other offense groups. This finding does not suggest that they commit shoplifting by chance. Sixty- five percent reported that the benefits of associating with peers were primarily informal socialization and talking. On the other hand, 44 percent of the subjects complained that they tend to perpetrate delinquent acts with less restraint when they are in groups. An examination of 20 kinds of self-reported delinquency revealed that group members perpetrated much more delinquency in groups than they did alone; however, they experienced slightly more such behavior with the same members arrested together than with other peers. The experience rate or prevalence rate varied by offense-type groups and among behavioral items. The experience rates of shoplifting group members were low except for shoplifting (61 percent). On the other hand, those of glue- sniffing groups were high throughout all behaviors. (English summary modified)