Volatile anaesthetics (VA) are different from other anaesthetic drugs as they are given via respiratory route. A special device (vaporiser) is attached to anaesthetic circuit to deliver VA. The target organ for VA is brain. To reach there, VA has to pass through anaesthetic circuit, lungs, and blood. This affects the concentration in brain. Amount of VA reaching brain affects the onset of induction of anaesthesia. Pharmacokinetics of VA are discussed. Pharmacodynamics of the VA are also listed including their effect on cardiovascular system, respiratory system, central nervous system, renal system, and liver. Metabolism of different VA like halothane, sevoflurane, desflurane, etc. is also elaborated upon. The chapter also discusses nitrous oxide, its manufacturing, its storage/commercial preparation, its properties, its mechanism of action, and closed gas spaces.