 Dexmedetomidine is a highly selective α2 receptor agonist, which produces sedative, anxiolytic and analgesic effects without causing clinically significant respiratory depression. Dexmedetomidine also reduces the propofol requirement for sedation and anaesthesia induction. Therefore, dexmedetomidine may be a useful co-induction agent to facilitate LMA insertion with minimal effects on respiratory function. A recent study showed that dexmedetomidine administration prior to propofol induction provided similar conditions for successful LMA insertion, as does fentanyl without respiratory depression. The purpose of this study was to determine the median effective dose ED50 of dexmedetomidine required for successful LMA insertion during induction with propofol of 2 mgkg . 