Rice mutants containing low levels of the 16-kDa allergenic protein, which is the main allergen in the rice grain for patients of atopic dermatitis due to the intake of rice, were screened, and 4 independent mutant lines with small amounts of this protein were found by SDS gel electrophoresis and immunoblot analysis. These mutants were grouped into two types. Two mutant lines, 85KG-4 and 86RG-18, contained low levels of the 16k-Da and 26-kDa polypeptides and a high level of the 57-kDa polypeptide. The 16-kDa polypeptide content of these mutants was about half that of the original cultivars. Homozygous lines were developed, and these showed normal growth and seed set. The other 2 mutant lines, 87KG-970 and 89WPKE-149, showed traces of the 16-kDa and 26 kDa polypeptides and contained a high level of the 13 kDa polypeptide. The homozygous plants of this type were sterile. All of the mutant lines had floury endosperms. Genetic analysis suggested that low 16-kDa polypeptide content is controlled by a single recessive gene. Attempts to separate of the genes for low 16-kDa polypeptide content and floury endosperm by crossing with the original cultivar were unsuccessful, suggesting the tight linkage of these two genes or pleiotropism of a single mutated gene. The relationship between low 16-kDa polypeptide content and the floury character and the possible use of the mutant as a low allergen rice are discussed.