BACKGROUND: NSAIDs (Nonsteroidal antiinflammatory drugs) had been known as having analgesic property and its mechanism is prostaglandin synthesis blocking action -peripheral mechanism-. Nowadays, central mechanism of NSAIDs were postulated by some animal or clinical studies, but the preemptive analgesic effects have been still in controversy. Thus, authors planned this study to evaluate whether NSAIDs have the preemptive analgesic effect by using propacetamol and ketorolac. METHODS: Seventy five patients undergoing laparoscopic vaginal hysterectomy were subjected and randomly allocated into three groups according to drugs given. Group P (n=25) and group K (n=25) were given propacetamol 2 gm or ketorolac 30 mg intravenous respectively at 15 minutes before induction. Group C (n=25) had no medication. Pain control using morphine were started in all three groups before skin incision. One anesthesiologist who didn't know which group the patients were allocated visited the patients when the patient arrived at recovery room after operation, postoperative 1 hour, 6 hours, 12 hours, 24 hours and 48 hours and estimated pain score and side effects. Parameters using pain score were visual analogue score (VAS; 100 mm) -subjective parameter- and Prince-Henry score (PHS) -objective parameter-. If VAS>50 or PHS>3, morphine 2.5 mg were given by i.v. and pain score were reestimated after 5 minutes and same dose of morphine were given until VAS<50 and PHS<3. RESULTS: Demographic data of three groups were insignificant. In group P, lower VAS, PHS and morphine consumption were observed than the other groups. Significant changes according to time were observed until postoperative 6 hours in each groups. Side effects occurred as nausea, vomiting and somnolence but statistical significance between groups were absent. CONCLUSIONS: Preoperative i.v. administration of propacetamol 2 gm in laparoscopic vaginal hysterectomy could have preemptive analgesic effects. But we think that determining the proper dosage and timing of administration that could have preemptive analgesic effect of NSAIDs are subjects demands further study.