Background: Although obsessive-compulsive disorder (OCD) has been found to be the 10th leading cause of disability of all medical conditions in the industrialized world, comparatively little is known about psychosocial functioning and quality of life (QOL) in OCD, particularly with regard to their relationship with symptom severity. Method: Quality of life and psychosocial function of 197 adults were assessed as part of a larger intake interview for a 5-year prospective study of OCD course. Two self-report measures (the Quality of Life Enjoyment and the Medical Outcomes Survey 36-Item Short-Form Health Survey) and 2 clinician-rated measures (the Range of Impaired Functioning Tool and the Social and Occupational Functioning Assessment Scale), each with established reliability and validity, were administered. Symptom severity was assessed with the Yale-Brown Obsessive-Compulsive Scale (YBOCS). Results: Quality of life was significantly impaired compared with published community norms with large effect sizes found for all domains assessed. The correlations (r) between all QOL measures and the YBOCS total score were significant, ranging from 0.40 to 0.77. Correlations between the YBOCS obsessions subscore and QOL measures were higher than those found between the YBOCS compulsions subscore and QOL. Insight as measured by the Brown Assessment of Beliefs Scale was significantly correlated with 5 of the 7 measures, although more modestly than the YBOCS correlations (r = 0.22 to 0.37). Subjects with a YBOCS score of 20 or higher had significant decline in QOL compared with those subjects with YBOCS scores lower than 20. Severity of obsessions and depressive symptoms, as well as marital status, were significant predictors of impairment in QOL. Conclusions: These findings indicate that all aspects of QOL are markedly affected in individuals with OCD and are associated with OCD severity (particularly obsessional severity) and depression severity. Exploratory results suggest that QOL and psychosocial functioning begins to be more significantly affected at YBOCS scores higher than 20. This score might be considered as a threshold criterion for OCD for Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.