This study examined chronic pain in adults with an intellectual disability (ID), in terms of its prevalence, impact on physical and psychological functioning, and treatments used. Questionnaires were distributed to 2378 primary caregivers (caregivers) of community-dwelling adults with an ID. The questionnaires were used to gather data on demographics, general health, nature of pain, impact of pain, treatment, and health-related decision making. Responses were received from 753 caregivers (31.6% response rate). Caregivers reported that 15.4% of this sample was experiencing chronic pain, for an average of 6.3 years. Significantly more females than males were reported to experience chronic pain, although age, communication ability, and level of ID were not found to be associated with the presence of pain. However, the presence of pain was associated with cerebral palsy, physical disability, and reports of challenging behaviour. A significant proportion of individuals with chronic pain also experienced limitations in several aspects of daily living, and more than 78% of caregivers reported that the service user had become upset or distressed by pain. More than 80% of service users were receiving some form of treatment for their pain, with most seeing a family physician and using analgesics as the primary form of pain treatment. Results indicate that chronic pain is a significant problem for persons with an ID, with a proportion of service users living with daily pain for many years and experiencing limitations in daily functioning, emotional well-being, and quality of life. (C) 2011 International Association for the Study of Pain. Published by Elsevier B. V. All rights reserved.