The benefits of two dosing methods, patient-controlled analgesia (PCA) with morphine sulfate (MS) alone and PCA plus continuous infusion of morphine sulfate (PCA + CI) were clinically evaluated in a randomized, single-blinded study of 30 adult abdominal surgery patients. Doses were adjusted based on pain and sedation ratings. Respirations, pulse, blood pressure, pain and sedation ratings were assessed. Subjects rated their pain twice daily using a visual analog scale for 72 hr postoperatively. The subjects reported pain relief with both dosing regimens. No statistically significant differences between the groups were found in pain and sedation ratings, or length of time using the device, with the exception of a higher amount of MS used on postoperative day two by the infusion group (p less than 0.003). There seems to be a trend for the PCA + CI group to have less fluctuation in sedation between days and better pain control (as demonstrated by verbal and visual analog pain scores) on the third postoperative day. Statistical significance was not found, however. PCA plus continuous infusion of MS may be a beneficial approach to the management of postoperative pain in selected patients; studies to identify these patients need to be done.