This study describes an innovative clinical tool - the ORS/SRS - to improve clinical quality and the use of theory of change to evaluate the performance of the system following implementation. The setting is a large public substance abuse system, which implemented the Duncan & Miller CDOI model in all treatment modalities. Implementation occurred without evaluation in mind, and the challenge was to design an evaluation to assess the effects of the intervention. The theory of change approach was used to evaluate the project. This involved developing criteria for plausible attribution, the use of mediation analysis to systematically build up a case for attribution.#EvaluationUse #2011Conference #Alcohol,DrugAbuse,andMentalHealth #ProgramTheoryandTheoryDrivenEvaluation