In this article, the authors address the rationale for and uses of treatment integrity measurement in psychotherapy research, focusing on therapists' adherence and competence in trauma and posttraumatic stress disorder treatment research. The following issues are examined: (a) distinctions between adherence monitoring, performed contemporaneously with ongoing study treatments, and adherence evaluation, and the implications for outcomes analysis; (b) simultaneous measurement of adherence and competence; (c) selection of sessions for adherence/competence assessment and the need for concurrent outcome measurement, and (d) the association between therapist adherence, competence, alliance and treatment outcome. Recommendations regarding common problems in the implementation of adherence and competence measurement are made throughout. The article concludes with a summary of steps and considerations in decision-making with regard to treatment integrity.