Although obsessive-compulsive disorder (OCD) is among the most common of all psychiatric disorders, the diagnosis is frequently overlooked unless specific screening questions are asked by the treating physician. The obsessive thinking and compulsive behaviours that primarily characterize OCD can be found in other obsessive-compulsive "spectrum" disorders as well. These disorders affect a sizable percentage of the U.S. population and have thus become an increasing public health problem. Preliminary results from our comprehensive survey of OCD sufferers found significant impairments in quality of life and substantial costs associated with the morbidity and treatment of OCD. This is of particular interest to the primary care practitioner since these patients often present initially to primary care physicians, and early diagnosis and appropriate treatment can substantially improve outcome.