The frequency, severity, and disruptiveness of pain related by 667 cancer patients are reported. The patients, all seen at a comprehensive cancer center, had cancers of the breast, colon and rectum, prostate, or various gynecologic sites. As expected, the proportion of patients with pain varied according to primary site and according to degree of progression of the disease. Pain, when present, was often of at least moderate severity and was felt to interfere with patients' activity and enjoyment of life to a moderate to severe extent. Degree of interference with activity and enjoyment of life was greater when the pain was caused by cancer than when it had another cause. Implications of these findings for professional and lay education and for treatment are discussed.