OCD is defined by the Diagnostic and Statistical Manual of the Mental Disorders as including the presence of obsessions that contain "persistent ideas, thoughts, impulses or images that are experienced, at least initially, as intrusive and senseless..." OCD symptoms can be placed on a continuum from mild to extreme. Although there has been conflicting research on the correlation of OCD and substance abuse, the most common belief of the experts is that OCD has been underdiagnosed within the substance abuse population. Most substance abuse treatment facilities employ staff who are not competently trained to detect and diagnose psychiatric illnesses in general and OCD specifically. The first step in successfully treating OCD within a substance abuse population is proper diagnosis. This article describes seven instruments used to diagnose OCD, as taken verbatim from Dattilio's practical guide on the treatment of OCD's. This is followed by descriptions of various treatment methods. They include exposure and response prevention, thought stopping, group therapy, and pharmacotherapy. An outcome study is described for the treatment of OCD/substance abuse, and implications are drawn for a county detention center. 8 references, a 24-item bibliography, and an appended screening test for OCD