Recently, experts have suggested that obsessive–compulsive disorder (OCD), a highly heterogeneous condition, is actually composed of distinct subtypes. Research to identify specific subtypes of OCD has focused primarily on symptom presentation. Subtype models have been proposed using factor analyses that yield dimensional systems of symptom categories, but not necessarily distinct subtypes. Other empirical work has considered the role of neuropsychological functioning and comorbidity as part of a comprehensive scheme for subtyping OCD. The identified dimensions from all of these studies have implications for the treatment of OCD. In this article, we review the research on subtypes of OCD, focusing on subtype schemes based upon overt symptom presentation and neuropsychological profiles. We also review research pertinent to alternative subtyping schemes, both conceptually and methodologically. The research is critically examined and implications for treatment are discussed. Recommendations for future investigations are offered.