Cognitive-behavioral therapy incorporating exposure and response prevention (ERP) is widely considered a first-line psychosocial treatment for patients with obsessive-compulsive disorder (OCD). However, a number of obstacles prevent many patients from receiving this treatment, and self-administered ERP may be a useful alternative or adjunct. Forty-one adult outpatients with a primary diagnosis of OCD, who reported at least 1 current or previous adequate medication trial, were randomly assigned to self-administered or therapist-administered ERP. Patients in both treatment conditions showed statistically and clinically significant symptom reduction. However, patients receiving therapist-administered ERP showed a superior response in terms of OCD symptoms and self-reported functional impairment. We discuss several potential reasons for the superiority of therapist-administered treatment, and propose a stepped-care integration of self-administered and therapist-administered interventions for OCD.