A clinicostatistical study was made on the first stage of surgery of dental implants in 204 cases with intravenous sedation during the past 3 years at the general dental office in order to analyze the effectiveness of Midazolam intravenous sedation with analgesic Butorphanol.<br/> The results were as follows:<br/> 1. Male patients were 59 cases (28.9%) and female 145 cases (71.1%). Age distribution was fifties 33.3% and forties 30.9%. Mean age was 52.011.0 years.<br/> 2. Preoperative complications were hypertension 25 cases and diabetes 12 cases. The prevaｌence rate of general diseases was 32.4%.<br/> 3. Dental implantation was devided into 3 blocks in the mandible and maxilla, and each jaw also divided into premolar-molar and incisor regions. The 1 block group consisted of 81 cases, mean 2.1 dental implants, mean operation time 54.3 minutes, 2 blocks group was 66 cases, mean 4.0 dental implants, mean operation time 92.0 minutes, and more than 3 blocks group was 57 cases, mean 6.0 dental implants, mean operation time 115.6 minutes.<br/> 4. The administration dose of Midazolam after injection of 1 mg of analgesic Butorphanol was 2.10 mg1.39 (0.028mg/kg) of 1 block group, 2.69 mg1.69 (0.041 mg/kg) of 2 blocks group, and 3.85 mg2.21 (0.055 mg/kg) of more than 3 blocks group. The mean dose of Midazolam was increased accompanied with increase of the number of operation blocks. The hemodynamics and respiratory condition during implantation were stable in each block group.<br/> 5. There was remarkable amnesia during the operation and some postoperative pain and swelling. There were no serious complications. There has been no falling and removal of dental implants.<br/> It is concluded that the effectiveness of Midazolam intravenous sedation with Butorphanol was remarkably high in dental implants operation.<br/>