The drag coefficient of the snow surface over the Antarctic Plateau is evaluated through direct measurement of Reynolds stress on the Mizuho Plateau, East Antarctica, in the austral summer. The estimated roughness height (Z0) varies from 10-1 to 10-4 cm, even under near-neutral conditions. Large shear stress appears in light wind, followed by increased turbulent intensity. In the katabatic wind region of the plateau, Z0 shows symmetric changes with wind direction. The average value of Z0 in the smoothest direction is 0.0004 cm, which is the minimum value previously reported, and it increases to 0.015 cm for 40¿ rotation of wind direction toward the roughest direction. The directional dependence of Z0 is similar at three stations located nearly 100 km apart. Unlike the results of Jackson and Carroll at the south pole, the smoothest direction deviates 20¿ from the mean sastrugi axes and agrees with the direction of the prevailing high wind. The 4-m neutral drag coefficient is estimated to be 0.8¿10-3 for the smoothest direction and 1.5¿10-3 for the roughest direction. The effect of snow drift is unimportant. A generalized discussion of the results is given in a companion paper. ¿ American Geophysical Union 1989