The authors review the literature on pain experience and pain assessment in people with cognitive impairments, focusing on individuals with dementia and mental retardation. The impact of cognitive impairments on pain sensation is not well understood, although some observations have been published. For example, research suggests that pain experience can be influenced by neuropathological processes in the brain and memory impairments. Reporting of pain decreases as cognitive impairment increases. In addition, poor verbal skills lead to difficulties in communicating pain. Pain assessment depends primarily on one's ability to describe the dimensions of pain. Individuals with limited ability to report pain can use pain assessment methods that rely on simple cognitive tasks. For individuals who have no ability to report pain, an outside observer must describe the discomfort experienced by interpreting the patient's body language. The authors conclude that further research is needed to develop valid and reliable assessment methods for people with cognitive impairments.