Sevoflurane and desflurane have important advantages over isoflurane and halothane. Disadvantages, which the clinician should keep in mind, include the degradation of both agents by soda lime under certain circumstances during closed circuit anaesthesia. As a result compound A and carbon monoxide (CO) may be generated in soda lime canisters and may be inhaled by patients. The extent to which this constitutes a significant problem during routine anaesthesia in humans is not clear. Recent developments in absorbent technology have the potential to reduce any hazard to negligible proportions. Other undesirable properties of the newer inhalation agents include agitation with sevoflurane in children and cardiovascular and airway effects with desflurane.