Our purpose was to determine whether an apparently healthy patient who died under general anaesthesia had malignant hyperpyrexia by examining her relatives and to suggest protective measures for the relatives of the deceased patient against this complication during future general anaesthetics. The family members of the deceased patient were examined systematically to determine whether or not they were prone to develop malignant hyperpyrexia. Raised serum CPK and aldolase levels, EMG changes, histopathological examination of the striated muscle, diminished muscle power during an ergometric test, and subjective symptoms revealed that other members of her family had muscular dystrophy. Our results support the theory that during general anaesthesia patients with muscular dystrophy are prone to develop malignant hyperpyrexia. Although muscular dystrophy is uncommon in Finland, affected persons should be catalogued, and preventive measures against malignant hyperpyrexia taken if they ever have to have a general anaesthetic.