Outcome measures often overlook client engagement in the dynamic process of change. Engagement of clients in treatment can be considered a measure of successful treatment, despite imperfect behavioral outcomes. The Epoch Counseling Center was 1 of 10 sites across the United States participating in the adolescent treatment models (ATM) program. The ATM program was designed to evaluate the effectiveness of promising adolescent substance abuse programs, to develop treatment manuals for these interventions, and to disseminate those that are shown to be effective. Epoch’s adolescent program was a 20-week group-based outpatient substance abuse treatment program consisting of 4 introductory drug education sessions and 15 skills building sessions. For the quantitative component of the study, adolescents received a comprehensive behavioral and psychosocial assessment with follow-up assessments 6 and 12 months thereafter focused on substance use, criminal involvement, and psychosocial adjustment. A total of 194 adolescents ages 14 to 18 participated in the quantitative evaluation. For the ethnographic component of the study, 25 adolescents were recruited from the quantitative study sample for in-depth, open-ended interviews. With the pervasiveness of navigation and coerced treatment, measuring engagement in the treatment process is an important variable for evaluating the success of a treatment program. The benefit of navigation is that clients tend to stay in treatment, despite the source of their motivation. The longer a client stays in treatment, the more opportunities he or she has to engage. The challenge is to find ways to move clients from navigation to engagement. The more often a treatment program does this the more successful it is. The process of treatment must be observed and success evaluated by those most closely involved. A general model that ties outcome evaluation more directly to the details of program experience is developed and presented. 1 table, 30 references