Fifty Hong Kong Chinese patients between 20-40 years, of ASA Gd I, undergoing third molar extraction were randomly allocated into two groups. For conscious sedation, to supplement local anaesthesia, one group received intravenous diazepam and the other intravenous midazolam. The majority in the study had never heard of intravenous sedation being available to supplement local anaesthesia during dental surgery and when given the chance to experience this method the majority found it highly acceptable. None preferred general anaesthesia for dental surgery. In this study midazolam had more advantages to the patient than diazepam; quicker onset of sedation, less pain during injection, profound anterograde amnesia and fewer postoperative complications being the main features. However, both drugs produced good operating conditions. Incidence of thrombophlebitis was low with both drugs, and may be so in Chinese compared with non-Chinese.