Four strains of Cl. sporo genes and 52 strains belonging to 6 types of Cl. botulinum were studied comparatively. Particularly, three noticeable characteristics, such as toxin production, proteolytic ability and thiaminase production, were examined. All the strains of Cl. sporo genes and of type A of Cl. botulinum were proteolytic and produced thiaminase I. All of the proteolytic strains of type B and F also produced thiaminase I. On the contrary, all the strains of type C, D and E were non-proteolytic and did not produce thiaminase. The non-proteolytic strains belonging to the type B and F of Cl. botulinum did not produce thiaminase.