Advanced dementia patients may be at substantial risk for undetected or undertreated pain. To examine the treatment of pain following hip fracture, a prospective cohort study was conducted in an academic teaching hospital. Fifty-nine cognitively intact elderly patients with hip fracture and 38 patients with hip fracture and advanced dementia were assessed daily. The cognitively intact patients rated their pain on a numeric scale ranging from 0 (none) to 4 (very severe). Analgesics prescribed and administered were recorded and compared to hip fracture patients with advanced dementia. The advanced dementia patients received one-third the amount of morphine sulfate equivalents as the cognitively intact patients. Forty-four percent of cognitively intact individuals reported severe to very severe pain preoperatively and 42% reported similar pain postoperatively. Half the cognitively intact patients who experienced moderate to very severe pain were prescribed inadequate analgesia for their level of pain. Eighty-three percent of cognitively intact patients and 76% of dementia patients did not receive a standing order for an analgesic agent. These data reveal that a majority of elderly hip fracture patients experienced undertreated pain. The fact that advanced dementia patients received one-third the amount of opioid analgesia as compared to cognitively intact subjects-40% of whom reported severe pain postoperatively-suggests that the majority of dementia patients were in severe pain postoperatively. This study and others suggest that directed interventions to improve pain detection and alter physician prescribing practices in the cognitively impaired are needed.