The author made a clinical study of postoperative respiratory function and analgesic effect of intrathecal morphine HCI which had been administered to 40 of a total 80 adult male and female patients who underwent abdorminal operation with spinal anesthesia from March, 1980 to September, 1981 at Department of Anesthesiology, Pusan National University Hospital. The results obtained were as follows: 1) Vital capacity during 6 to 12 hours after operation was significantly increased in patients given intrathecal morphine as compared with other groups of patients. 2) Patients given intrathecal morphine showed a significant increase in tidal volume during 6 hours after operation. 3) There was no significant change in the level of arterial oxygen tension at pre-and postoperative period in all groups of patients. 4) The average duration of postoperative analgesia was 33.6 and 33.8 hours respectively in patients who were given intrathecal morphine.