Gang Resistance Education and Training (G.R.E.A.T.) is a 9-hour gang prevention program administered by uniformed law enforcement officers to middle-school aged youths. This report summarizes results of a 5-year study of the program. The study revealed that G.R.E.A.T. has modest positive effects on adolescents' attitudes and delinquency risk factors but no effects on their involvement in gangs and actual delinquent behaviors.