In order to estimate the tooth-age by degree of attrition, the author has studied 605 stone models from 1996 to 1997. All of the attrition were classified and analyzed by 8 degrees. The result were as follows : 1. The degree of attrition in male was higher than that in female for same age group and especially, canine and first premolar showed the most prominent difference in sex. 2. The most severe attrition in posterior teeth was first molar followed by second molar, first premolar and second premolar in decreasing order of sequence. 3. The coefficient of correlation and relation equations by the degree of attrition were obtained.