The purpose of the present research was to predict, from the results of rig test, the amount of wear on exhaust valve seats in durability testing of gasoline engines. In the rig test, measurements were made of the wear loss ratios in a number of cases in which a number of factors in valve seat wear were within a certain range. The results for factors of high sensitivity were further used to create an equation for calculating the amount of wear. The amounts of wear calculated from the equation for calculating the amount of wear and from driving modes of actual engines were found from the results to show a high correlation with the amount of wear in bench tests and the amount of wear in vehicle tests. The influence of differing valve seat materials and valve diameters was also determined by rig test, indicating that the amount of wear in actual engines could be estimated.