Forty patients having surgery requiring muscle paralysis and tracheal intubation were randomly allocated to receive either halothane (n = 20) or sevoflurane (n = 20). Following intravenous anaesthesia and tracheal intubation, inhalation induction of anaesthesia was simulated. After attaining an end-tidal anaesthetic concentration of 2 MAC for the respective agent, the airway was obstructed for 3 min. The end-tidal anaesthetic concentration was measured for the first three breaths following the period of airway obstruction. The decrease in alveolar concentration of sevoflurane following 3 min of airway obstruction was found to be significantly greater than that of halothane. We conclude that even if the airway obstructs completely during inhalational induction of general anaesthesia, awakening would be faster with sevoflurane than with halothane.