Two lines of rice, Tankei 1915 and 2019 with a low amylose content were registered as breeding materials in 1992. There lines were selected in the progeny following the treatment of the Japanese rice cultivars, Kinmaze and Kochihibiki with methyl-nitroso-urea (MNU). Tankei 1915 was characterized by a dull endosperm which could be distinguished from waxy and nonwaxy endosperms. The amylose content of Tankei 1915 was 9.2%, half of the content of the parental cultivar, Kinmaze. The line harbors the du-1 gene which is responsible for lowering the amylose content and is located at a locus independent of the waxy (wx) locus on Chromo some 6. The other line, Tankei 2019, was characterized by a dull endosperm which is visually similar to the waxy endosperm. The amylose content of Tankei 2019 was 6.3%, one-third of the content of the parental cultivar, Kochihibiki. This line harbors the du-2 gene which is responsible for the decrease of the amylose content and is located at a locus independent of the wx and du-1 loci. The new type of endosperm starch of rice grains may contribute to the improvement of the eating quality of cooked rice and the development of new products in the food industry.