This paper reports on the development and initial psychometric evaluation of the Treatment Adherence Survey-patient version (TAS-P), a brief instrument designed to assess patient adherence to Cognitive-Behavioral Therapy (CBT) and pharmacotherapy recommendations for OCD. Eighty individuals with Obsessive Compulsive Disorder (OCD) were administered the TAS-P as part of the intake interview of a prospective, observational study of the course of OCD. Results demonstrated excellent test-retest reliability. Responses on the TAS-P were also significantly correlated with scores on a self-report measure of general treatment adherence and with data collected from a chart-review, demonstrating concurrent validity. Treatment adherence was not explained by demographic variables. However, participants who reported nonadherence to CBT recommendations had more severe OCD symptoms at the time of intake than those who did not endorse CBT nonadherence (mean Y-BOCS = 23.27 +/- 7.5 versus 18.20 +/- 8.0, respectively). Results suggest that the TAS-P is a promising instrument for assessing reasons for nonadherence to recommendations for CBT and pharmacotherapy interventions.