This paper describes the extent to which communities implementing the Communities That Care (CTC) prevention system adopt, replicate with fidelity, and sustain programs shown to be effective in reducing adolescent drug use, delinquency, and other problem behaviors. Data were collected from directors of community-based agencies and coalitions, school principals, service providers, and teachers, all of whom participated in a randomized, controlled evaluation of CTC in 24 communities. The results indicated significantly increased use and sustainability of tested, effective prevention programs in the 12 CTC intervention communities compared to the 12 control communities, during the active phase of the research project when training, technical assistance, and funding were provided to intervention sites, and 2 years following provision of such resources. At both time points, intervention communities also delivered prevention services to a significantly greater number of children and parents. The quality of implementation was high in both conditions, with only one significant difference: CTC sites were significantly more likely than control sites to monitor the quality of implementation during the sustainability phase of the project.