Casts are often transferred to the articulator by arbitrary means, because the method of locating the true hinge axis point thought to be a complicated and time consuming procedure, and because the importance and significance of the true hinge axis in the construction of dental prosthesis is not sufficiently understood. In this report, the author constructed the hinge axis locator and determined the variations in location of the true hinge axis points from the location of the hinge axis point determined by arbitrary means. For this report, the procedure was followed on 50 persons with normal occlusion and sound T.M.J. function, so 100 true hinge axis points were recorded and compared with the arbitrary hinge axis point. The results obtained were as follows. 1. The mean distance from the arbitrary hinge axis point to the true hinge axis point was as follows. Right; (O)5.17mm., (V)3.44mm., (H)3.55mm.. Left; (O)5.63mm., (V)3.95mm., (H)3.51mm.. 2. The percentage of true hinge axis points classified at intervals of 2mm was as follows. 0-2mm; 4%, 2-4mm; 21%, 4-6mm; 37%, 6-8mm; 26%, 8-10mm; 10%, Over 10mm; 2%. And only 50% of the 100 true hinge axis points were located within a 5mm. radius of the arbitrary hinge axis point. 3. Instead of transferring the casts to the articulator by arbitrary means, the careful location of the true hinge axis points is recommended to avoid potential sources of error in mounting casts.