The Compulsive, Impulsive and Anxiety Disorders Program at the Mount Sinai School of Medicine is conducting a study of Topiramate (Topamax) added to an SSRI for the management of treatment-resistant Obsessive-Compulsive Disorder. The purpose of the study is to evaluate the safety and efficacy of Topiramate versus placebo added to a selective serotonin reuptake inhibitor (SRI) in patients with treatment resistant OCD. The program is 12 weeks in duration and involves regular visits with a psychiatrist as well as complete psychiatric and medical evaluations. Treatment and medication for the study will be provided free of charge.Participants must be between the ages of 18 and 65 and have an onset of OCD at least 1 year prior to screening. In addition, participants must be taking a clinically effective dose of an SSRI for at least 3 months and must maintain their current dose throughout the study. Participants must not have a primary OCD symptom of hoarding.