OBJECTIVE: Continuous treatment teams serving persons with co-occurring severe mental disorders and substance abuse disorders at seven sites in New Hampshire were evaluated to determine their fidelity to a model based on the Program for Assertive Community Treatment. METHODS: Continuous treatment teams and standard case management programs at the seven sites were evaluated on 13 criteria for fidelity to the continuous treatment team model over a 27-month period. Data sources included clinicians' activity logs, agencies' management information systems, interviews, observation of staff activity and practices, and clinical records and other documents. RESULTS: The continuous treatment teams scored significantly higher than the case management programs on ten of the 13 criteria. The teams were more effective than the case management programs in implementing substance abuse treatment. CONCLUSIONS: Evaluation of the programs' fidelity to the model criteria allowed differentiation of successfully implemented continuous treatment teams from standard case management and from an unsuccessfully implemented team. The results confirm the need for careful measurement of model implementation and for investigation of organizational issues such as administrative support and clarity of program mission.