Several recent qualitative studies suggested that sex composition of gangs helped shape the gang experience for both boys and girls. In this study, there was a sample of 369 gang members including youths in gangs with varied sex compositions. Approximately 45 percent of male gang members described their gangs as having a majority of male members; 38 percent said their gangs were sex-balanced; 16 percent were in all-male gangs; and less than one percent reported being in gangs that were majority-female. Young women were more likely than were young men to describe belonging to sex-balanced, rather than majority-male gangs. The membership appeared to be fairly evenly split between those claiming core and noncore positions within their gangs. However, fewer females in majority-male gangs reported holding central positions in their gangs than did girls in other gang types. Males in all-male gangs reported the lowest levels of gang organization and males in sex-balanced gangs the highest. Membership in a gang with a minority of female members and a majority of males was correlated with higher rates of delinquency for both males and females. It was notable that girls in majority-male gangs were more delinquent than were boys in all-male gangs. Findings supported organizational sociologists’ assertion that some differences often attributed to gender or cultural differences between males and females were more appropriately attributable to group structure. They also were consistent with the observations of qualitative studies that the sex composition of gangs, independent of sex, played an important part in shaping the norms and activities of gangs and their members. Just as other gang research indicates the importance of considering such factors as geographic location, organizational structure, and age, these findings highlight the significance of the gang’s sex structure. 5 tables, 16 notes, 55 references.