The most frequently used postoperative analgesia techniques are intramuscular injection (IM) and patient controlled analgesia (PCA). Recently, the use of epidural catheter injection (EPI) has been done with success. This study was done to prospectively compare these three techniques for postoperative analgesia after extensive operations upon the colon and rectum. Patients were randomized to one of three analgesia groups--IM, intramuscular morphine sulfate; PCA, patient controlled morphine sulfate, and EPI, epidural morphine sulfate. Data collected included age, time to first bowel movement, amount of narcotic, number achieving 75 per cent of preoperative forced vital capacity, postoperative pruritus, headache, nausea and vomiting, respiratory depression, atelectasis or pneumonitis. A visual analog pain scale was used to evaluate postoperative pain severity (0, no; 1, partial; 2, marked, and 3, total relief). Sixty-eight patients were eligible for study (IM, 19; PCA, 22; EPI, 23, and excluded, four). The EPI group required significantly less daily narcotic compared with either the IM or PCA groups (17.0 +/- 6.12 milligrams; 67.8 +/- 26.8 milligrams; 40.5 +/- 20.6 milligrams, respectively, less than 0.05 ANOVA) and total narcotic (81.3 +/- 31.3 milligrams; 355.4 +/- 147.7 milligrams; 215.3 +/- 105.4 milligrams, respectively, p less than 0.05 ANOVA). EPI achieves excellent pain control in more patients with a significantly lower dose of narcotics and significantly fewer pulmonary complications. Therefore, epidural analgesia is the optimal method of postoperative analgesia after extensive abdominal operations.