The authors report on development, reliability, and findings of the Psychosocial Treatments Interview (PTI) to assess treatments reported by patients in a naturalistic study of the longitudinal course of anxiety disorders. The PTI ascertains frequency of different types of psychosocial treatments, based on patients' reports. The PTI showed good internal consistency and very good interrater reliability. At first 6-month follow-up, the most common modalities were supportive, medication discussion, and dynamic intervention. Combinations were common. Delivery of treatments differed by site. Overall, the PTI fills a methodological need for the assessment of the treatments reported by patients in naturalistic follow-up studies.