BACKGROUND: Recent studies suggest the hypothesis that blockade of nociceptive input with local anesthetics before surgery can decrease pain beyond the immediate postoperative period. The purpose of this study was to determine if the preincisional infiltration with local anesthetics affected postoperative pain relief. METHOD: Among 30 patients having tonsillectomy, 15 patients(group 1) given peritonsillar infiltration using lidocaine with epinephrine(1 : 200,000) were compared with 15 patients(group 2)given peritonsillar infiltration using saline with epinephrine(1 : 200,000). Following general anesthesia with a mixture of O2-N2O(50%) and enflurane(1-2vol.%), peritonsillar infiltration were performed 5 minutes before surgery. Constant incisional pain and pain on swallowing were assessed using a visual analogue scale at 4 hour, 1, 2, 3 and 4 days postoperatively. The time to emergence and behaviour of patient at 0.5, 1 and 4 hour were recorded postoperatively. RESULT: Preincisional infiltration with lidocaine resulted in a significant decrease in postoperative pain during 4 days after surgery and smoother emergence. CONCLUSION: There were significant difference in pain scores between lidocaine group and saline group during 4 days after surgery. Preincisional lidocaine infiltration seemed to have analgesic activity beyond the residual anesthetic period. The results of this study support the theory of pre-emptive analgesia.