The aim of this study was to evaluate the analgesic efficacy and side effects of intrathecal morphine in the dose range 0.2-0.5 mg. One-hundred patients scheduled for elective lower limb orthopedic operation under spinal anesthesia using hyperbaric or isobaric bupivacaine 0.5% with morphine in dose from 0.2 to 0.5 mg. Pain score, duration of analgesia and the incidence of adverse effects like nausea, vomiting, pruritus, urinary retention and respiratory depression were assessed for 48 hr postoperatively. There were significant differences in the duration and efficacy analgesia and the incidence of pruritus the morphine dose-related. We did not observe the increased frequency of nausea and vomiting with increased dose. The respiratory depression not observed in connection with intrathecal morphine. The evidence from this current study suggests that spinal anesthesia with combination of local anesthetic and morphine can be employed to provide safe and efficacious analgesia in patients undergoing orthopedic operations. The adverse effects which developed due to intrathecal morphine were able to treat with success.