Report 1.The authors intended to study what shades showed the Japanese teeth. It has been compared with the tooth shade guides as a method, because the tooth shade guides are only a standard comparison system made experimentally and sensorily in shades. However, there are no optical connections between them. We can't obtained, therefore, any chracteristic groups from values measured by the tooth shade guides, and we can't conclude the characters of these samples, that is, the average and the deviation value and so forth.At the beginning of our study, we tried to analyse the optical characters of the tooth shade guides of S. S. W. & Co, in U. S. A, with the automatic recording spectrophotometer of the Central Laboratory, Hitachi Ltd (Japan) . In such a way the authors obtained the data showing the character of the tooth shade guides expressed in numeral.Report 2.Before the authors observed the characters of the Japanese tooth shades in different ages, we analyzed the optical characters of the tooth shade guides (S. S. W. & Co., U. S. A.) which is used for a standard, with the automatic recording spectrophotometer. (Report 1.)With this instrument we measured the Japanese tooth shades of 3, 431 examples in wide distribution of ages (2 to 76 years of age) . It results that the average values in the optical characters of the tooth shade variated characteristically as follows in every groups at the different ages :1) The chromaticity showed almost white at infancy stage, blueish at youth stage, and increased the reddish shade after manfood stage.2) The chromaticity of the deciduous teeth is more white than that of the permanent teeth, and we find the inflexion at point of about 10 years of age in chromaticity curve.3) There is no difference in averages of the chromaticity during groups of 10 to 30 years of age in statistics, so that groups in 10 to 30 years of age showed constant chromaticity.4) In the chromaticity curve respective averages of groups in more 30 years of age were different values, but every value tended to be reddish.5) In the luminosity it became darker, with a constant velocity, as the age advances from the youth stage to the old age stage.6) At 30 to 35 years of age, the luminosity curve, such as the chromaticity curve, showed the second point of inflexion tended darker rapidly than that of groups of younger ages.7) It has been considered that respectively second points of inflexion in both chromaticityand luminosity-curve show some basic biological meaning.