Intrathecal administration of morphine for pain relief became popular since Pert, et al (1973) reported the opioid receptors in spinal cord. It is obvious now morphine bas prolonged and profound analgesic effect with few compl-ications but the leant dose which produces sufficient analgsia with insignificant complication is still controversial. The dosage of intrathecal morphine used for postoperative analgesia has varied from 0.1 mg to 2 mg, but significantly low dosage was required br direct intrathecal route than by epidural one to reach the appropriate analgesic CSF concentration. We selected 60 Patients (50 for cesarean section, 10 for total hysterectomy) and divided into 3groups to compare the effects respectively. Group l : 20 patients receiving 0.05mg of intrathecal morphine, Group ll : 20 patients receiving 0.1 mg of intrathecal morphine, Group lll : 20 Patients receiving 0.2 mg of intrathecal morphine The results are as follows ; 1) The analgesic effects of group l and ll were good and similiar, but 2 of group l and 1 of group ll required a single supplementary intramuscular demerol 6 hours after intrathecal morphine injection. The quality of analgesia was judged to be better in group lll than in group I and ll. 2) The duration of analgesia of group lll was a little longer than group I and ll, which showed similar duration. 3) The side effects of group l, ll and lll were similar, but pruritus was noted twice as much in group in lll than in group l and ll.