Four rice (Oryza sativa L.) mutant lines lacking glutelin alpha-1 subunit were obtained by screening the progenies of fertilized egg treatment with MNU. SDS-PAGE and IEF analyses showed that the mutants without pI6.82 polypeptide in common while forming/increasing other polypeptide indicating that the mutants were controlled by structural genes. IEF analysis also suggested that the polypeptides of pI6.82 and pI8.58 derived from the same glutelin precursor. The mutants are considered to be useful material for glutelin quality improvement and for genetic regulatory mechanism study of glutelin biosynthesis.