People with intellectual or developmental disabilities suffer from the same chronic diseases and conditions as the general population but are more likely to have physical and psychological comorbidities. This places them at higher risk for experiencing pain and for having more frequent or severe pain. Self-report is the gold standard in pain assessment; but people with intellectual or developmental disabilities often cannot provide self-reports. Pain assessment in this population is therefore challenging. People with intellectual or developmental disabilities are increasingly being moved from institutions into community-based settings. Therefore, nurses in all settings need to be knowledgeable about alternate pain assessment methods. This article provides an overview of pain and pain assessment in this population, summarizes the relevant clinical research, and describes one facility's approach to pain assessment of its patients.