In view of the increasing frequency with which, during recent years, it has been shown that outbreaks of food poisoning affecting human beings and domestic animals or fowl have been caused by the ingestion ofB. botulinustoxin in canned foods, it was considered advisable to make an investigation of the resistance of the spores ofB. botulinusto various sterilizing agencies which are commonly employed in canning foods. Our interest in the problem was stimulated by the fact that in our investigations of a number of outbreaks of fatal poisoning which had occurred on the Pacific Coast,1,2it was found that practically all had been caused by the ingestion of home canned vegetables and fruits; and in investigating the methods of canning which had been employed in preserving the food it was found that no one method was at fault. Our investigations showed that foods which had been canned