Aim: The purpose of our study was to compare the effect of remifentanil and clonidine on peroperative stress response. Materials and Methods: Forty patients scheduled for abdominal surgery randomized to two groups. Anesthesia was induced by thiopentone 5-7 mg kg-1 and vecuronium 0.1 mg kg -1. Desflurane 3.6% and 50% N2O-O2 used for the maintenance of anesthesia. In group I (n=20) remifentanil 1 μg kg -1 was administered as a bolus dose during the induction of anesthesia and an infusion dose of 0.1 μg kg-1 min-1 was used during the peroperative period. In group II (n=20) clonidine 4 μg kg-1 was infused in 20 minutes during the induction of anesthesia and clonidine infusion at a rate of 2 μg kg-1 hr-1 was used in the peroperative period. In the preoperative, peroperative and postoperative periods EKG, systolic, diastolic and mean arterial pressures, heart rates, peripheral oxygen saturation were recorded and blood glucose, cortisol levels were analyzed. Results: There was no significant difference in terms of patient data, operation time, extubation time, hemodynamic parameters and glucose-cortisol levels in the preoperative period (p>0.05). Peroperative glucose-cortisol levels were in normal ranges in remifentanil group, but in clonidine group these levels were higher than normal levels (p<0.05). During the postoperative period these levels were higher from the control values in both groups (p<0.05). There was a significant difference in modified Ramsay scale (p<0.05). Nine patients in remifentanyl group and 1 patient in clonidine group had nausea (p<0.01). The time for first analgesic requirement was earlier in remifentanil group (p<0.05). Conclusion: Remifentanil during desflurane anesthesia may provide stable conditions until the extubation time. Postoperative hemodynamic unstability and early analgesic necessity are the disadvantages of this agent. Clonidine may delay the time for analgesic requirement in postoperative period.