 2. Subjects must continue to experience clinically significant symptoms of OCD Y-BOCS score 19 and a rating of moderate or greater on the Clinical Global Impressions CGI scale despite at least two adequate SRI monotherapy trials. One unsatisfactory trial can include the SRI currently being taken by the patient provided that the duration of treatment is 12 weeks or more and that the dose has been adequate. Subjects must be taking a clinically effective dose of a SRI i.e., clomipramine, citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine and sertraline for at least 12 weeks. Subjects must be on their current dose for at least 12 weeks and must maintain their current dose throughout the study. 