The carbon content of the tyre tested is about 0.69% and that of the rail, which engages with the tyre is three kinds-0.53%, 0.71% and 0.08%. The test was conducted for two different cases, i. e. Case 1. Both rail and tyre are not hardened. Case 2. One of them is hardened. And in each case the test was conducted under two different conditions-with and without lubrication, using an Amsler-type abrasion testing machine. The following are the findings resulted from the present test : 1) When neither of rail nor tyre is treated, the test under dry condition has revealed that if the carbon content of rain exceeds that of tyre, the degree or mutual defacement is samall. 2) When either rail or tyre whose carbon content is higher than the other is hardened, the test under dry condition has revealed that the hardening effect somewhat increases over the original state. 3) Under lubrication, if either rail or tyre is hardened, the effect is so remarkable in all combination.