The blast resistoance of the numerous rice varieties amounting to almost four hundreds which are native to the different latitudinal regions in Asia has been compared by means of the artificial inoculation in the glass house as well as by considering the data obtained from the natural infection in the field. So far as the leaf-blast resistance is concerned, the variety-groups which are separated according to the habitats can be classified into following three categories. (1) The variety-groups, all of which show infection-type A. (vid. fig. 1). Variety-groups of Japanese lowland, “Hôrai” (Japanese lowland type bred in Formosa), and North China are involved herein. (2) The variety-groups which reveal a striking intervarietal variation as regards the infection-type (i. e. from A to F). Variety-groups of Japanese upland, Formosan upland (in the mountain regions), middle & South China, and Europe & America are involved. (3) The variety-groups which exhibit a moderate intervarietal variation as regards the infection type (i. e. from B to F). Variety-groups of Eormosan endemic (except upland), Philippines, Celebes, Great & Lesser Sundas, French Indo-China, Siam, Burma and India are involved. Considering the above-named data, it seems that the Japanese lowland group is consisted of the closely related varieties which might have been originated from certain allied genes, but it is of almost no doubt that the variety-groups other than the Japanese lowland are mixed with the varieties different in their genetic constitution. So far as the percentage of ear-and node-blast infection is concerned, such a marked difference as evidenced in the leaf-blast resistance was not found between the temperate and tropical group. In general, however, the percentage of neck blast infection was lower in many of the variety-groups native to the tropical region than in those to the temperate, though that of the node-blast infection was often opposed to the above.