A late development model of the Tec 6 vaporizer for the administration of desflurane vapour has been evaluated. It is heated electrically and has both electronic monitors of vaporizer function and alarms. The new filling system is a significant improvement over previous Tec filling systems. The vaporizer requires a warm-up period before it may be used, but when activated it provides an output that is approximately linear between 1 and 18% vapour concentrations, at flow rates between 200 ml min-1 and 10 litre min-1.