The author observed the effects of an intravenous drip of ketamine hydrochloride to 60 patients with in high surgical risk who had undergone abdominal surgery at Pusan National University Hospital from March, 1981 to February, 1982. The results obtained were follows. 1) Average duration of anesthesia was 148 minutes and the rate of intravenous drip of ketamine was ranged from 0.017 to 0.02mg/kg/min. Total dose of ketamine was 264.2mg on and average. 2) Significant increase in blood pressure and heart rate was observed in the ketamine drip group during the operation (p<0.05). 3) Changes in values of arterial blood gas analysis during ketamine drip were within normal limits. 4) Duration from anesthesis to awakening in recovery room was longer in ketamine drip group than thiopental-halothane group. 5) Psychotomimetic symptoms after ketamin administration included convulsions, discomfort, and hallucinations etc. and diazepam premedcation could not completely relieve the above symptoms. 6) Relief of postoperative incisiional pain was excellent in ketamine drip group.