The occurrence of serious accidents in complex industrial systems such as at Three Mile Island and Bhopal has prompted development of new models of causation and investigation of disasters. These analytical models have potential relevance in anaesthesia. We therefore applied one of the previously described systems to the investigation of an anaesthetic accident. The model chosen describes two kinds of failures, both of which must be sought. The first group, active failures, consists of mistakes made by practitioners in the provision of care. The second group, latent failures, represents flaws in the administrative and productive system. The model emphasizes the search for latent failures and shows that prevention of active failures alone is insufficient to avoid further accidents if latent failures persist unchanged. These key features and the utility of this model are illustrated by application to a case of aspiration of gastric contents. While four active failures were recognized, an equal number of latent failures also became apparent. The identification of both types of failures permitted the formulation of recommendations to avoid further occurrences. Thus this model of accident causation can provide a useful mechanism to investigate and possibly prevent anaesthetic accidents.