Data collection and analysis were done separately for the two agencies because of differences in departmental structures and practices. A total of 512 LASD homicide cases were examined, and 300 LAPD cases were considered. Data on gang and nongang homicides were distinguished according to variables pertaining to setting, participants, and incidents. Investigative impacts on the gang and nongang designations of homicides were examined according to the number of interviews pertaining to the case, the number of suspects charged, and arrests. The study performed bivariate analysis of investigative variables, bivariate analyses over time, and multiple regression analysis. With minor qualifications, analyses of the LAPD and LASD data indicate that gang designations of homicides reflect characteristics of the incident settings and participants. The investigative processes did not significantly impact the homicide designations. Gang homicide rates reported by these departments can thus be used as reasonable criteria for evaluating the effectiveness of various interventions to reduce gang-related homicides. 18 references and 8 tables.