A longitudinal, intensive treatment program is described that was implemented over an 8-year period in a community-based setting for a young man with mental retardation and oppositional defiant disorder with severe physical aggression. The development of this disorder and its systematic treatment are described, with new components added based on improvement in the individual’s behavior. The individual made steady progress and has maintained good behavioral stability for the final three years of the treatment program. This paper highlights the inherent difficulties of applying empirically validated treatment strategies in community-based settings.