An analysis has been made of the deaths which occurred during or shortly following anaesthesia at the St. Boniface General Hospital from 1949 to 1964 inclusive. Contributory factors due to anaesthesia, surgery, and pre-existing disease were considered. It was found that in almost 70 per cent of the fatalities, death was due to factors not related to anaesthetics. In fact, in only 15.6 per cent of the cases could it be determined that death was due purely to anaesthetic causes. It was also shown, on further breakdown into two eight-year periods, that a marked decrease took place in the number of deaths related to anaesthesia. The deaths dropped from an incidence of 1:4477 in the earlier period to 1:9728 in the later period. It was felt that this improvement was due mainly to the institution of a supervised postanaesthetic recovery room, the provision for a “float” anaesthetist, and repeated searching reviews of anaesthetic complications and operating room mortality.