In continuation of previous investigations1 issued from the Danish State Serum Institute, I have carried out some systematic studies on the occurrence of the Bordet-Gengou bacillus. Since 1916, this institute has employed the coughingplate method introduced by Adolph H. Meyer for the bacteriologic diagnosis of whooping cough, and in Denmark this method is being used more and more. Previously the results from a total of 2,811 suitable specimens have been compiled. In addition, I have examined 1,086 suitable specimens at the State Serum Institute during the period from Sept. 1, 1930, to March 1, 1931. All told, the material consists of 3,897 specimens, 2,144 of which came from pertussis patients. The results from these 2,144 examinations are given in table 1. From the material of the serum institute it is difficult to say anything definite as to the occurrence of the Bordet-Gengou bacillus in the later stages of whooping