Inclusion Criteria:

1. outpatients with a primary DSM-IV diagnosis of OCD
2. age 18-40 years, inclusive
3. moderate to severe symptoms of OCD: a) YBOCS score of ≥24; b) CGI-Severity ≥4; c) significant disruption of daily activities (≥2 on item 1 or 6 of the YBOCS); d) disruption of employment/education function (≥2 on item 2 or 7 of the YBOCS)
4. if not on SSRI, must: a) have discontinued treatment with an SSRI at least 12 weeks prior to study Day 1; b) or be treatment naïve.
5. if on SSRI: a) must have residual symptoms despite a three month trial of an adequate dose of an SSRI drug; b) must currently be on an SSRI for at least 16 weeks and on a stable regimen for at least 8 weeks prior to Day 1.
6. Competent to give informed consent.

Exclusion Criteria:

1. moderate to severe depression (MADRS >25)
2. significant risk of suicidal behavior at screening
3. surgical lesion of anterior capsule (capsulotomy) or cingulate gyrus (cingulotomy)
4. co-morbid tics, Tourette syndrome, schizo-obsessive disorder, pure obsessive disorder or Axis II disorder
5. first degree relative with Tourette syndrome
6. pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS)
7. current cognitive behavioral psychotherapy
8. history of sensitivity to any of the ingredients in the study drug
9. Clinically significant abnormality in any screening laboratory results
10. Clinically significant organic disease (other than OCD), including cardiovascular, hepatic, pulmonary, neurologic, or renal disease, or other medical condition, serious intercurrent illness, or extenuating circumstances that, in the opinion of the Investigator, would interfere with the performance or interpretability of, or put the patient at risk from, the study procedures
11. a current, active or ongoing DSM-IV Axis I psychiatric disorder other than anxiety disorders, major depression, dysthymia, and depression not otherwise specified (but including organic mental syndromes or disorders and dementia) as long as these are secondary diagnoses.
12. women who are pregnant, breastfeeding, or refuse to use adequate birth control
13. diagnosis of alcohol or substance abuse and/or dependence in the past 6 months
14. participating in an investigational drug study within 28 days of Day 1
15. concomitantly using any psychotropic medication other than SSRI or chloral hydrate for sleep
16. receiving treatment with a monoamine oxidase inhibitor within 2 weeks, a depot neuroleptic within 6 months, or a neuroleptic, anxiolytic, or antidepressant on a daily basis in the 2 weeks prior to Day 1.