The prevalence and clinical correlates of substance use disorders (SUDs) were examined in a clinical sample of Obsessive Compulsive Disorder (OCD). As part of their intake interview into an observational study of the course of OCD, 323 participants completed a battery of standardized measures. Twenty-seven percent of the sample met lifetime criteria for a SUD. 70% of participants with comorbid SUDs reported that OCD preceded SUD onset by at least one year. Younger age at OCD onset and presence of Borderline Personality Disorder (BPD) were each associated with increased risk of alcohol use disorders but only BPD was associated with increased risk of drug use disorders. SUDs affect more than one-quarter of individuals who seek treatment for OCD. Individuals with a juvenile-onset of OCD or comorbid BPD may be especially vulnerable to SUDs. Further research is needed to identify risk factors for SUDs and to better understand their impact on OCD course.