The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS: Goodman, Price, Rasmussen, Mazure, Fleischman, Hill, Heninger & Charney, 1989a, b, Archives of General Psychiatry, 46, 1006–1016), a widely used measure of obsessions and compulsions, is typically used by summing the items to yield a global measure of symptom severity. However obsessive-compulsive disorder (OCD) is characterized by two distinct groups of symptoms (i.e. obsessions and compulsions), and so it was hypothesized that OCD, as assessed by the Y-BOCS, may be two dimensional. In other words, the items assessing obsessions may be factorially distinct from the items assessing compulsions. A confirmatory factor analysis (CFA) was conducted using responses from 83 OCD patients to determine whether OCD as assessed with the Y-BOCS is unidimensional or forms two distinct dimensions. Results supported a two-factor solution, and suggest that items assessing obsessions should be scored as one subscale, and items assessing compulsions scored as a separate subscale. Depression, as assessed by the Beck Depression Inventory, (Beck, Ward, Mendelsohn, Mock & Erbaugh, 1961, Archives of General Psychiatry, 4, 561–571), was correlated with both subscales. Trait anxiety, as assessed by the State-Trait Anxiety Inventory (Speilberger, 1983, Manual for the State-Trait Anxiety Inventory (Form Y). Palo-Alto, CA: Consulting Psychologists Press), was correlated with the obsessions subscale but not with the compulsions subscale.