The relation between caries incidence and sugar consumption was cleared up by Takeuchi and Takahashi with the material of primary school children in Tokyo under the view point of the dental caries that should be observed by the rate of caries incidence as "one tooth as unit" and during a limited period, because the caries develop on the tooth as unit and never be healed spontaneously. The author, for the supplement study, observed the relation between sugar consumption and the rate of caries incidence during a year with a Cohort observation of the cases and analysed a pattern of the caries incidence in the first molar of 10,553 chidren who were born between 1924 and 1946, admitted into a school between 1931 and 1953 of 14 primary shools in Kyoo. The results were as follows: (1) Accumulated sugar consumption during the maturation period of teeth has only slight influence upon caries incidence.(2) The relation between sugar consumption for a year of new caries incidence in the first molar and the rate of new caries incidence for a year are extremely close and correlation coefficient of the average rate of caries incidence during 6-11 years of age to sugar consumption are: for example, in the lower first molar the year of the new caries incidence, the year before, and the year before last are respectively 0.8, 0.8 and 0.7. Also it was presumed that the type of quantitative relation on the semi-log graph shows a almost straight line. On this point this is almost as same as a results of Takeuch and Takahashi theoretically but it shows a little more slow curve and a smaller number. (3) With the materials during the years before the world war Ⅱ. I had made an age pattern of the rate of caries incidence in the first molar for 6-11 years of age. Using this pattern, I drew the model picture of the rate of caries incidence for a Cohort of which had a change of sugar consumption during the year. I had learned that it is possibly similar to the picture of the caries incidence for a year, which is drew with real Cohort. According to this result, with the model picture, I had learned the caries incidence for a year has extremely close relation with the sugar consumption during the year. Also it is presumed that an influence of the caries incidence on the individual tooth will always show a same age pattern without an influence of the sugar consumption.