A series of discriminant analyses revealed substantial differences between the participant characteristics and settings of the two types of cases. Compared to nongang incidents, cases of gang violence involved more participants, lower levels of suspect-victim relationship, lower ages, more male-only cases, and more minority group involvement. They also were more likely to occur in public places, involve cars and guns or other weapons, yield additional charges and victim injuries, and involve more unknown suspects and fears of retaliation. In addition to these discriminators, argot, turf designations, and special dress and behavioral cues also differentiated between gangs and nongangs. Evidence for an influence of police investigation and reporting procedures on these differences was weak. Finally, while findings pertain to both homicide and nonhomicide incidents, they apply more fully to homicide cases. Additional study materials are appended. Tables and 29 references. (Author abstract modified)