One-third of the sample had been arrested for motorcycle theft, one third for other types of delinquent behavior, one-eighth for violent crime, and the remainder for drug abuse and other crimes. Over 64 percent of the co-offending groups included 2 members, while only 6 percent were comprised of 5 or more members. Police officials estimated that only 15 percent of the groups had a designated leader. Many of the younger and smaller groups were involved in bicycle theft. Groups which committed theft through breaking and entering or violent crimes were more likely to be characterized by a large number of young members, had a high proportion of leaders, and exhibited a high degree of delinquency proneness.