Immunological reaction in blood serum of 340 cases, including healthy subjects, patients and pregnant womens with a new aerobic thiamine decomposing bacillus was performed with the following result. The positive percentage of agglutination reaction with a new thiamine decomposing bacillus and B. thiaminolyticus was 77% and 30%. No positive agglutination reaction with B. aneurinolyticus was seen. Therefore a new bacillus seemed to be widely distributed in human intestine and the most important bacterium resulting in thiaminase disease. According to many experimental results as previously reported and report in the present paper, a new bacillus can be determined perfectly to belong to a new species of Genus Bacillus different from B. thiaminolyticus in various points of view.