Background: Midazolam is often used as an anxiolytic premedication before surgery. Although the sedative, anxiolytic, and amnestic properties of midazolam may be desirable before the induction of general anesthesia, respiratory function is impaired frequently by larger doses of midazolam. Therefore, we evaluated the adequate doses of midazolam premedication on anxiolytic and sedation without its serious side effects. Methods: Eighty ASA I or II adult patients scheduled for elective minor surgery were randomly allocated to four groups according to premedication doses of midazolam. They were group 1: midazolam 0.05 mg/kg IM for lean body mass (LBM); group 2: midazolam 0.075 mg/kg IM for LBM; group 3: midazolam 0.1 mg/kg IM for LBM; group 4: midazolam 0.125 mg/kg IM for LBM. Blood pressure, heart rate, bispectral index (BIS), oxygen saturation (SpO2), anxiety visual analogue scale (VAS), and observers assessment of alertness and sedation (OAA/S) scores were measured before and at 30 minutes after midazolam premedication. The frequency of apnea, defined as a cessation of spontaneous respiration for more than 10 seconds, was recorded. Induction time and dose requirements in propofol-induced general anesthesia were recorded at the loss of opening their eyes on verbal command and eyelid reflex after starting the propofol-infusion. Following intubation, blood pressure and heart rate were measured. Results: The bispectral index and anxiety VAS was significantly decreaced in group 3 and group 4. However, oxygen saturation were significantly lower in group 4 compared with group 3. Conclusions: We concluded that group 3 (midazolam 0.1 mg/kg IM for LBM) is the proper premedication dosage for anxiolytic and sedation in Koreans without respiratory side effects. (Korean J Anesthesiol 2001; 41: 269-274)