The target community, West Place (a pseudonym), consists of 5 municipalities ranging in population from 25,000 to 80,000. Each of the five cities is the home of at least one Chicano youth gang, and the largest city has at least six Chicano youth gangs. Many local police officials fear that a close relationship exists between gangs within correctional institutions located near West Place and local youth gangs. This relationship is hypothesized to be an important factor contributing to youth gangs' delinquency behaviors. The prospective change agent in this community is Chicano Services, Inc. (CSI), a private, nonprofit community-based organization. The behavior-ecological model can be viewed as an extension of behavior analysis and the methods of behavior modification to systems other than the individual client. The study demonstrated the use of this model to diagnose a community problem and to generate interventions. A systematic replication of Stumphauzer's previous work was accomplished, and behavioral methods were successfully established as the basis for CSI's gang delinquent treatment and prevention programs. A total of 14 reference notes, about 25 references, and 1 table are appended.