The tibiofemoral angle is widely used for the diagnosis and treatment of knee problems, especially in degenerative joint disease of the knee. Among the various methods of measurement of tibiofemoral angle, Bauers method is being used most frequently. But measurement by Bauers method has seemed to show wide individual differences. Therefore we designed a ruler which can be used very easily for the measurement of the tibiofemoral angle with little differences between persons who measure the angle. To testify the advantages of our method, we selected 4 orthopedic surgeons and let them measure the tibiofemoral angles of 60 knees of 30 patients by Bauers method and by our method using the ruler. And 20 orthopedic surgeons measured tibiofemoval angles of 2 left knees by Bauers method and by our method using the ruler. The values of the tibiofemoral angle by two methods were compared and analyzed statistically. There was no significant differences between mean values. But, the tibiofemoral angles by our new method showed little differences among measurers. (P <0.05)