Statistical reliability of the Treatment Perceptions Survey (TPS) questionnaire was examined using data from 19 California counties. The 14-item TPS was designed for clients receiving substance use disorder services at publicly funded community-based programs. The TPS is being used for evaluation of the State's 1115 Medicaid Waiver, external quality review of county-based systems of care, and quality improvement efforts. The survey addresses four domains of access to care, quality of care, care coordination, and general satisfaction that each include multiple items, plus a single item focused on self-reported outcome. Reliability test results of the four domains as composite measures were statistically significant. General satisfaction ratings were the best predictor of self-reported outcome in a path analysis model, followed by ratings of care coordination and quality of care. Separate analyses of TPS data from clients receiving specialty mental health services suggest the questionnaire can also be used reliably in mental health settings.