PURPOSE: An adequate pain control is one of important factors for obtaining good outcomes in the ambulatory basis of hemorrhoidectomy. There have been many methods for pain control after hemorrhoidectomy such as narcotics, various kinds of analgesics, etc. The aim of this study is to compare intraoperative internal anal sphincter injection of Ketorolac tromethamine and other two conventional methods for pain control. METHODS: A total of 56 patients with hemorrhoid grade III or IV underwent surgery between May and October 1999, and prospectively assigned to three groups in the consecutive order. The group was divided in Group 1: [Ketorolac tromethamine (Tarasyn) 60 mg intrasphincteric injection intraoperatively and 30 mg IM/prn?10 mg po/6hrs], Group 2: [No intraoperative injection and maintain pain control with Tarasyn 30 mg IM/prn/10 mg po/6hrs], and Group 3: [No intraoperative injection and maintain pain control with Pethidine (Demerol) 50 mg IM/prn and Ibuprofen 400 mg/Paracetamol 500 mg/Codeine 20 mg (Myprodol) po/8hrs]. The post operative data and pain scoring was performed on the questionnaire with Point box scale (BS-11) and Behavioral rating scale (BRS-6) each 24 hours during 5 days after surgery. RESULTS: There are 22 patients in the Group 1, 16 in the Group 2 and 18 patients in the Group 3. The median age of the Group 1 is 42.5, Group 2, 44.5 and Group 3, 45 years. The pain score on the first day after surgery in group 1 was significantly lower than group 2 (p<0.05) in the both pain scoring scale but was no differences between group 1 and 3. On the fifth day after surgery group 3 was significantly lower than both group 1 and 2 in the point box scale (p<0.05). The urinary retention rate and the day of first bowel movement after surgery show no differences among three groups (p>0.05). CONCLUSIONS: Intraoperative internal anal sphincter injection of Ketorolac tromethamine shows a better pain control than conventional methods in early postoperative period. Therefore it might be helpful for patients to go home on the day after surgery, and strong pain killer to control pain after discharge will be needed.