In keeping with NIJ's mission of generating research-based knowledge that can inform policy and benefit practitioners, this Research Report presents a broad-based collection of papers representative of NIJ's portfolio of gang-related research. It emphasizes program evaluation. Evaluations often indicate the efficacy and/or shortcomings of a program; in either case, the information can be applied by those seeking solutions to similar problems. The Report examines gang-related field, survey, and records research in the interest of gender, race/ethnicity, and criminal justice system interventions.