Evaluated retrospective therapist ratings of the flexibility used when applying the procedures and strategies prescribed in the treatment manual. Flexibility ratings were collected from 18 therapists who had treated 148 children with anxiety disorders (ages 9 through 13). Analyses revealed strong reliabilities for a flexibility questionnaire and that flexibility was used by therapists; however, significant relations between therapist-rated flexibility and treatment outcome were not found. Discussion focuses on the role of flexibility in manual-based psychological treatments and future directions for study.