Though patient-controlled analgesia (PCA) has been in use for over a decade, it has been popularized only recently. Conventional techniques of intermittent intramuscular (IM) administration of analgesia have fallen short of meeting the needs of patients following major abdominal surgery. This has prompted a search for methods to improve postoperative pain management. Though PCA has been accepted in many hospitals, few studies comparing conventional IM administration of morphine with PCA have been performed. A prospective randomized study comparing IM- and PCA-administered morphine in 62 patients undergoing colon surgery was performed. A comparison of the efficacy of analgesia and extent of sedation using these approaches shows that PCA allows for analgesia with less sedation and less drug requirement than that of IM administration. No differences were noted in postoperative duration of ileus, duration of hospitalization, and total hospital costs. This study confirms the safety and efficacy of PCA, and should be considered the current optimal method of controlling pain following major colonic surgery.