The very first anaesthetics were gaseous. These early slow, irritant or flammable drugs were ultimately displaced by intravenous agents, despite other beneficial properties. Preliminary work with two new insoluble, potentially rapid-acting nonflammable anaesthetics showed desflurane, the less soluble, to be too irritant while sevoflurane was smooth and well-tolerated. This thesis set out to examine possible clinical andlor financial benefits from the use of sevoflurane in day case patients. A double-blind comparison showed sevoflurane to induce anaesthesia almost as rapidly as the most common intravenous drug, but to minimise apnoea and hypotension, with a smoother transition to the maintenance phase and faster emergence from brief day case anaesthesia. While a few patients found gaseous induction unpleasant, this was not confirmed by an audit of sevoflurane's more widespread use. Further work evaluated alternative, vital capacity, induction techniques. However, simple tidal breathing was found to be equally effective but more consistent, appearing to be the method of choice, even compared with the most recent, optimised delivery of intravenous anaesthetics. Gaseous induction was shown to facilitate airway maintenance with either a face mask or laryngeal mask. Double-blind comparisons showed that it also provided acceptable conditions for tracheal intubation in the small minority of day case patients in whom this is required. Compared to the usual intravenous anaesthetic, gaseous induction with sevoflurane was shown to be less expensive under most common circumstances. Gaseous induction also reduced anaesthetic consumption during the subsequent maintenance phase, making it the most efficient way in which to use inhalation anaesthetics. Having reestablished gaseous induction as an important technique with clinical and financial benefits in modem day case practice, this thesis concludes with suggestions for future research to further refine the process and find solutions to some minor problems, such as occasional patient reticence and the possibility of increased postoperative nausea.