This report gives some results obtained from the actual measurement of tractive resistance, fuel consumption rate and vibration of a 3 ton crawler type tractor & sulky (see Table 2), engaged in hauling logs or trees at non-steep mountain-side areas of our mountain forest.<br> 1. The actual tension acting on the skidding wire rope and the fuel consumption rate of the engine for the tractor at load or no load, have been measured, when logs or trees (species of Japanese Larch) skidded on the forest land of several ten meters length from the felling point to the tractor road-side, by the small one-drum type winch mounted on the back-part of this tractor. This result is shown in Table 3 & Fig. 3.<br> 2. The fuel consumption rate of engine for the tractor, engaged in hauling trees on the tractor road having 3_??_13% gradient, at the running speed of 2.5_??_6.0km/hr, is shown in Fig. 4.<br> 3. The author has been able to measure the tensions acting on both skidding wire rope and traction rod of running tractor & sulky, at the same time, by means of the measuring method designed by the author, shown in Fig. 1. This mechanism for the traction of logs is that which characterizes the log-transportation by tractor & sulky, different from other hauling methods, and this test result is shown in Table 4-a, b & Fig. 5.<br> 4. From this result, it is observed that the tension acting on the traction rod is smaller at its absolute value and has more variable repeated stress than the tension acting on the skidding wire rope. The author considers that this test needs to be continued further, and this result indicates that something is needed for the improvement of the mechanical structure and operation system of logging tractor & sulky, since the body of this sulky is liable to lose balance on rough ground owing to the highness of the center of gravity.<br> 5. The gross acceleration in the vibration of the driver's seat-frame for this tractor did not appear at hauling logs or trees by this tractor & sulky on the soft earth road. It is observed that the number of impact is smaller and the acceleration is greater at its absolute value in proportion as the tractor runs faster and that the number of impact of three components at running on each forest road (speed=6.2km/hr) is equally ranked as: the component of to and fro > the one of right and left > the one of up and down, provided that a tractor only with bulldozer runs on hard forest road paved with gravel, at the speed of 2_??_6.2km/hr (see Table 5)