During the past 12 years the Oregon Social Learning Center has been studying the application of social learning theory to aggressive children. One result has been the development of a treatment program in which parents are trained to alter their child's behavior. That program has been evaluated on three separate samples of aggressive children. Those tests, however, were conducted with treatment performed by the research staff. The paper reports on the current work in implementing that program in three real-world mental health agencies and evaluating its effectiveness with agency families. The current evaluation includes the following: (a) an analysis of the competence of the social learning-trained therapists in conducting the program; (b) random assignment of client families to either a social learning-trained therapist or a member of the staff not trained; (c) multiple measures of client outcome including in-home observations of the child and his family using an observation system of demonstrated reliability; (d) other measures include parental symptom reports, and questionnaires from therapists, parents, teachers, referral agents, and physicians; and (e) one year posttreatment follow-up. The article gives further description of the treatment program and the evaluation strategy. (Author)