Objective. Effective postoperative pain control reduces postoperative morbidity. In this study, we investigated the effects of intrathecal morphine, ketamine, and their combination with bupivacaine for postoperative analgesia in major abdominal cancer surgery. Study Design. Prospective, randomized, doubleblind. Setting. Academic medical center. Patients and Methods. Ninety ASA I–III patients age 30 to 50 years were divided randomly into three groups: the morphine group (group M) received 10mg of hyperbaric bupivacaine 0.5% in 2mL volume and 0.3mg morphine in 1mL volume intrathecally. The ketamine group (group K) received 0.1 mg/kg ketamine in 1mL volume instead of morphine. The morphine1ketamine group (group K1M) received both 0.3mg morphine and 0.1mg/kg ketamine in 1mL volume intrathecally. Postoperative total morphine consumption, first request of analgesia, visual analog score (VAS), and side effects were recorded. Results. Total PCA morphine was significantly decreased in group M1K compared with groups M and K. Time to first request of analgesia was prolonged in groups M and M1K compared with group K (P 0.001). VAS in group M1K was reduced from two to 24 hours, and in group M from 12 and 18 hours postoperation compared with group K, with an overall good analgesia in the three groups. Sedation was significantly higher in group M1K compared with group M until six hours postoperation. No other side effects were observed. Conclusions. Adding intrathecal ketamine 0.1mg/kg to morphine 0.3mg in patients who underwent major abdominal cancer surgery reduced the total postoperative morphine consumption in comparison with either drug alone, with an overall good postoperative analgesia in all groups, with no side effects apart from sedation.