Obsessive-compulsive disorder (OCD) is a chronic and debilitating condition that is relatively common in both children and adults, and it is associated with a wide range of functional impairments. Mental health researchers and practitioners have placed considerable attention on OCD over the past two decades, with the goal of advancing treatment and understanding its etiology. Until recently, it was unknown to what extent this disorder was associated with functional impairment. However, recent research shows that the condition has significant social and occupational liabilities. This article discusses etiology, common symptom presentations (including comorbid and ancillary symptoms), basic OCD subtypes, neuropsychological functioning, and the relation these have with functional disability in OCD. Recommendations for future research are also considered.