The purpose of the treatment after dental examination for school children must be applicable effectively and adequately to school education and its administration incorporating dental subjects.<BR>For the present study, attempt was made to serve as an aid to health-promotion of school children by means of authors' new idea on statistical treatment to satisfy the above purpose.<BR>As the materials of the present study, a total of 953 school children of a certain elementary school in Tokyo were subjected to the dental examination in April, 1961, their ages ranged from 6 to 11, and the teeth examined have amounted to a total of 19, 713 deciduous and permanent teeth.<BR>These materials were divided into the group of all members and the group classified by each age.<BR>The teeth were divided into deciduous teeth and premanent teeth, and each of them was classified by tooth, then, observation was made on def and DMF teeth.<BR>The results obtained were as follows.<BR>1. The percentage of children with one or more def teeth was 74.50 per cent, and percentage of children with one or more DMF teeth was 74.60 per cent. Average number of def teeth per child was 4.33, and that of DMF teeth was 2.1.<BR>In view of the group classified by each age, there observed a tendency that def teeth were decreasing and DMF teeth were increasing in the advancement of their ages.<BR>Percentage of teeth with one or more def teeth was 59.25 per cent, and the percentage of teeth with one or more DMF teeth was 16.20 per cent. Both showed an increasing tendency in the advancement of their ages.<BR>2. The following shows each percentage of the possessors classified by tooth; as regards def teeth on the upper jaw, central deciduous incisors - 12.90 per cent, lateral deciduous incisors - 19.20 per cent, deciduous canines - 27.38 per cent, the first deciduous molars - 41.86 per cent and the second deciduous molars - 61.59 per cent; while as to the lower jaw, central deciduous incisors - 2.20 per cent, lateral deciduous incisors 4.51 per cent, deciduous canines - 24.02 per cent, the first deciduous molars - 47.84 per cent and the second deciduous molars - 47.53 per cent.<BR>As for DMF teeth on the upper jaw, central incisors - 1.78 per cent, lateral incisors - 1.57 per cent, the first premolars - 4.72 per cent, the second premolars - 8.18 per cent, the first molars - 42.18 per cent and the second molars - 3.48 per cent: as regards the lower jaw, central incisors - 1.15 per cent, lateral incisors - 1.25 per cent, the premolars - 1.04 per cent, the second premolars - 2.20 per cent, the first molars - 72.08 per cent, the second molars 20.93 per cent, and there observed no canine tooth on both the upper and lower jaws.<BR>In view of the group classified by each age, def teeth showed a decreasing tendency, and DMF teeth showed an increasing tendency.<BR>3. As regards the relationship between each value on the number of def teeth and DMF teeth in the group classified by each age, the relationships between def and DMF teeth numbers were observed on the basis of the percentage of possessors obtained in most easy way, as the results, significant or highly significant correlations were observed on the percentage of the possessors of def, the average number of def teeth per child, def canines on both the upper and lower jaws, the first deciduous molars and the second deciduous molars on def, and also on the percentage of the possessors of DMF, average number of DMF teeth per child, and the first molars of the upper and lower jaws on DMF.<BR>These relations were expressed in the equations of straight and curve regression, and so regression straight and curve can be obtained, therefore, simplification was achieved on each value of def teeth.