Teams at several universities collaborated in studies of the Causes and Correlates of Delinquency program in three cities. This bulletin presents the findings from the Rochester (New York) Youth Development Study (RYDS) concerning the contributions of youth gang membership to delinquency. The RYDS started with a sample of 1,000 boys and girls in the 7th and 8th grades of the Rochester public schools. The sample included more youth from high-crime areas and fewer from low-crime areas. About 30% of the youth in the study reported being a member of a street gang at some point. Results clearly indicate that gang members were responsible for most of the delinquent acts reported. Although gang members were only one-third of the RYDS respondents, they were responsible for 86% of the serious delinquent acts, 69% of the violent acts, and 70% of the drug sales. These findings underline the importance of establishing effective intervention programs for gang-involved youth. The Office of Juvenile Justice and Delinquency Prevention (OJJDP) implemented a comprehensive response to gangs in 1994, with initiatives that include the identification of promising programs to reduce gang involvement. The Boys & Girls Clubs of America's Gang Prevention through Targeted Outreach program is an example of a gang reduction effort that is succeeding by recruiting youth into youth clubs in a nonstigmatizing way. Building its programs on a solid base of empirical research enables the OJJDP to plan multifaceted responses to youth gangs. (Contains 10 references.) (SLD)