Few studies have explored the phenomenon of pain in people with severe cognitive impairment. Pain assessment, which depends primarily on people's ability to describe dimensions of pain, becomes problematic when clients' cognitive impairment is so severe they cannot respond to pain assessment tools. The purpose of this study was to describe the phenomenon of pain for a subgroup of aggressive cognitively impaired nursing home residents who were enrolled in a larger study of aggressive behavior. To determine if pain was a possible factor influencing aggression, information was sought from five sources: family members, nursing assistant (NA) caregivers, medical record listings of pain-related diagnoses, use of analgesics, and observations of aggressive behaviors. Families reported pain in 44% of subjects, while NAs reported pain in 66% of subjects. Seventy-six percent of subjects had one or more pain-causing diagnoses. Sixty-four percent of subjects whose family members thought they may have pain were being treated with analgesics, compared to 44% of subjects whose NA reported they may be experiencing pain. Aggression scores were significantly higher in subjects who had two or more pain-related diagnoses and in subjects with arthritis. Nurses who are aware of a history of pain, reports of pain by families and caregivers, presence of pain-related medical diagnoses, and who realize pain may be a trigger for aggressive behavior may be more likely to recognize pain in cognitively impaired older adults. Better pain assessment should lead to improved treatment of pain in this population.