BACKGROUND: Premedication traditionally has several goals: reduction of anxiety,pain, and secretions and provision of basal or background sedation. The purpose of this study was to evaluate the efficacy and side effects of nalbuphine, midazolam and buprenorphine as premedication agents. METHODS: Two hundred thirty three patients who were scheduled to have an elective operation were included in this randomized, double-blind study. Nalbuphine 0.2 mg/kg, midazolam 0.05 mg/kg or buprenorphine 0.005 mg/kg was given intramuscularly with atropine(0.01 mg/kg) one hour before arriving at operating room. Sedation, level of anxiety, subjective rating on the effect of premedication and side effects including emesis and etc. were evaluated. RESULTS: The sedation score and the level of anxiety were not significantly different among three groups. The subjective rating on the effect of premedication was significantly higher in midazolam group than other two groups(p<0.05). The frequency of preoperative emesis was not significantly different among three group. The frequency of postoperative emesis was significantly higher in buprenorphine group than other two groups(p<0.05). Buprenorphine group showed dizziness and flushing more frequently than the other two groups(p<0.05). CONCLUSION: The present study demonstrated that, as a premedicant, midazolam increase the patient's satisfaction and decrease lessen the incidence of postoperative emesis and buprenorphine increase the incidence the side effects such as postoerative emesis, dizziness and flushing.