The volatile inhalation anaesthetics have been implicated in a variety of adverse viscerotoxic reactions. In general, they have been proven to produce very few non-predicted toxicities. Hepatitis caused by halothane now seems to be the only major problem in this regard with these drugs in current practice. The evidence is convincing that this reaction is based initially on biotransformation. Thus decreases in the amount of biotransformation and lessened production of reactive metabolic products would theoretically produce a safer anaesthetic. While not perfect in all circumstances, enflurane and isoflurane come close to achieving the goal of decreased adverse viscerotoxic events.