Fourteen cases of myxoedema crisis have been reportedand 93 additional cases have been collected from the literature. Hypothermia, coma and shock have been identified as the main clinical features of crisis. It has been pointed out that while clouding of consciousness is universal, coma is of doubtful prognostic significance. The importance of hypothermia in prognosis has been stressed. Various stress factors have been described which may initiate crisis especially respiratory infections and epileptic fits. The urgency of adequate treatment has been emphasised but overenthusiastic treatment is only slightly less dangerous than delay and inadequate treatment. However, even the best available treatment will only lead to a moderate improvement in outlook and the only successful way is prevention.