This document provides information on treatment integrity and how to ensure it. It defines treatment integrity as a multidimensional construct that involves both the content and process of how an intervention is implemented. It discusses assessing treatment integrity using methods that examine adherence, exposure, errors of omission/commission, and differentiation between programs. Barriers to integrity like intervention complexity and implementer characteristics are reviewed. Specific strategies are presented to measure integrity, including developing tools that rate operationalized intervention steps. The importance of participant responsiveness and intervention characteristics are also covered.