[Clin Psychol Sci Prac 18: 148–153, 2011]
Treatment integrity, also known as treatment fidelity, is integral for empirical testing of intervention efficacy, as it allows for unambiguous interpretations of the obtained results. Ensuring treatment integrity is also important for dissemination of evidence-based practices and quality improvement of services. However, in the examination of the relationship between treatment integrity and treatment outcome, it is important to consider that treatment integrity may be a proxy variable for other variables impacting therapeutic change (e.g., characteristics of intervention, clients, setting, and therapist). Considerations on examining the association between integrity and outcome are discussed. Further, recommendations on the level to which treatment integrity needs to be addressed in psychotherapy research and clinical practice are provided.