Few studies have been made on mechanisms of race walking from the biomechanical points of view. In the present study the mechanism of prope1ling in race walking was examined by comparing electromyogram activities of race walkers observed in 30m race walking with those of normal adults observed in 30m natural walking. Electromyogams were recorded from ten muscles of lower limb, two shou1der muscles and two trunk muscles with surface electrodes, 5mm in diameter, using 25m recording wires. Both walkings were done on the ordinary levelground. Subjects were five male race walkers and two normal adults. It was found that the hip joint was adducted at the beginning of the stance phase, and then abducted and strongly extended simultaneously at the later period of the stance phase in race walking while neither of these occurred in natural walking. This finding suggests that propelling of race walking is attributable dominantly to the abduction and extention of hip joint followed by its adduction. The adduction would be effective in absorbing the shock occurring when the foot touched the ground. It was pointed out that the mechanism of "hip adduction and hip abduction-extension" constitute the characteristic pelvis movements so conspicuously observed in race walking.