Relatives frequently accommodate patients' obsessive-compulsive symptoms and clinicians hypothesize that such accommodations adversely affect patient outcome. This study's purpose was to develop a valid and reliable measure, the Family Accommodation Scale for Obsessive-Compulsive Disorder (FAS), and to investigate the family accommodation construct. We administered the FAS and additional family and patient measures to 36 adult obsessive-compulsive patients and their primary caregivers. The FAS demonstrated excellent interrater reliability and good internal consistency and performed well on assessment of its convergent and discriminant validity. Family accommodation was significantly associated with patient symptom severity and functioning, and with relatives' own obsessive-compulsive symptoms. Although most relatives accommodated patient symptoms, many did not believe that such accommodations improved the patient's clinical status. The FAS will provide researchers and clinicians with a useful tool for assessing family accommodation and for identifying families who may benefit from interventions aimed at developing more adaptive coping strategies.