Objective: Given the present emphasis on accountability and maintaining quality, the objective of this study was to develop, apply, and assess the reliability of a fidelity rating instrument for consumer-operated services--a promising model, but one for which fidelity criteria are not yet established. Method: Based on observations, documents, and director interviews from 31 consumer-run drop-in centers, we developed a scale measuring fidelity to pre-established criteria and rated each center on scale items. A second study examined the interrater reliability of the measure. Results: Scale scores on the 31 centers showed substantial heterogeneity on the majority of the criteria. The fidelity rating scale demonstrated satisfactory interrater reliability on most items. Conclusions: The fidelity rating instrument is ready to be used by social work researchers evaluating consumer-operated services. Furthermore, social work researchers can use similar methods with other innovative services that should be evaluated but currently lack standards and fidelity criteria. (Contains 4 tables.)