A prospective survey was undertaken to determine the prevalence and characteristics of breakthrough pain in cancer patients admitted to a hospice. Of 414 consecutive admissions, 33 patients were confused ol too unwell to take part and 136 were pain-free The remaining 245 reported 404 pains (range 1-5 per patient); of these patients, 218 (89%) had breakthrough pain and identified 361 pains (range 1-5 per patient). Breakthrough pain was classified as somatic (46%) visceral (30%), neuropathic (10%) or mixed etiology (16%). Thirty-eight percent of pains were severe or excruciating. The average number of daily breakthrough pain episodes was 7 (range 1-14); 49% occurred suddenly. Most (59%) were unpredictable, and 72% lasted less than 30 minutes. Seventy-five percent of patients were dissatisfied with their pain control. Breakthrough pain is common among patients admitted to our hospice. It is frequent, short lasting; often unpredictable and not necessarily related to chronic pain making treatment difficult. (C) U.S. Cancer Pain Relief Committee, 2000.