The author collected 93 male stone model and 93 female stone model of upper and lower jaw of the koreans as samples and studied the degree of attrition with age increase. Determining the degree of attrition, each normal cusp were given 40 points and calibrated into percentage. The percentage score were examined and analized, and came to the following conclusions. 1) Increased age were found graudually higher the degree of attrition at 10 to 20 age,. The degree of attrition presented localized disappearance of marginal-ridges and marginal grooves. At 30 up to 40 age, about 40 to 50% of the degree of attrition were found gradually on cusp ridges and grooves At 50 to 60 age, it was found about 70 to 80% of attrition. 2) Male score was slightly higher than female. 3) There was no significant difference between male and female score.