The authors selected 24 original papers which were regarded them as the epidemiological study and the statistical study from their titles, from the end of World War II to 1981. And these papers were selected from 3 medical journals of internal medicine, other medical journals and proceedings of 2 International Conferences (see Table 1), and also were the object of study, namely, theoretical considerations. Besides we classified these 24 papers into 2 sorts; papers for an epidemiological study and a statistical study, and made a comparative study of details of these papers theoretically. As the result we were able to clarify what the authors of 24 papers had considered about the natures of epidemiology and statistics as the science. It was clarified that two sciences, epidemiology and statistics, had been in the general trend without any recognition of the differences between two. And as the conclusion we pointed out that the field of activity of statistics was broader than that of epidemiology, and the nature of statistics as the science might be changeable according to the object, moreover, statistical theory might be a branch of mathematics and so on.