Background: Dexmedetomidine is an alpha₂ - adrenergic agonist with sedative andanalgesic properties. This study aimed to investigate if the use of continuous dexmedetomidine infusion with i.v. morphine patient-controlled analgesia (PCA) could improve postoperative analgesia while reducing opioid consumption and opioid-related side effects. Materials & methods: In this prospective randomized, double-blinded, controlled study, 24 patients with obstructive sleep apnea syndrome undergoing uvulopalatopharyngoplasty were assigned to two groups. Group D received a loading dose of dexmedetomidine 1µg kgˉ¹  i.v., 30 min before the anticipated end of surgery, followed by a continuous infusion at a rate of 0.6 µg  kgˉ¹ hrˉ¹ for 24 hr. Group P received a volume-matched bolus and infusion of placebo. In both groups, postoperative pain was initially controlled by i.v. morphine titration and then PCA with morphine.  Cumulative PCA morphine consumption, pain intensities, sedation scores, cardiovascular and respiratory variables and narcotic-related adverse effects were recorded for 48 h after operation. Results: Extubation time was significantly prolonged in dexmedetomidine group (16±7 vs. 11±6 min p=0.074) in the placebo group. Visual analogue scale scores were significantly greater during the first 2h after tracheal extubation in the placebo group than in the dexmedetomidine group. The time to first analgesic request was significantly longer in the dexmedetomidine group than in the placebo group (21±11 vs. 9±4min; p=0.002). Compared with group P, patients in group D required 52.7% less morphine by PCA during the first 24h postoperative period, whereas levels of sedation were similar between the 2 groups at each observational time point. Fewer patients in group D experienced nausea and vomiting than those in group P (P< 0.05). There was no bradycardia, hypotension, or respiratory depression. Continuous dexmedetomidine infusion may be a useful anesthetic adjuvant for patients who are susceptible to narcotic-induced respiratory depression. Conclusion: Continuous infusion of dexmedetomidine for pain relief after uvulopalatopharyngoplasty significantly reduces the amount of PCA morphine used by the patients postoperatively without affecting their ventilatory parameters and was associated with fewer morphine-related side effects. This novel drug could become a useful anesthetic adjuvant for patients with obstructive sleep apnea who are susceptible to narcotic-induced respiratory depression.