Summary: We have analyzed HLA gene frequencies and HLA haplotype (HLA-A, -B, -DR) frequencies of the registered donors in the Japanese unrelated bone marrow donor registry. Simultaneously, HLA gene frequencies, and haplotype frequencies of HLA-A, -B, and -DR antigens in the donors who registered in 47 different prefectures were calculated, and examined that any distribution differences of HLA gene frequencies, and the frequencies of HLA haplotypes might exist. In some prefectures, the frequencies of some HLA haplotypes were shown to be distributed more frequently than the other prefectures. When we compared Japanese HLA haplotypes with those in the populations in the our neighborhood countries, it was disclosed that Japanese and Korean shared 6 haplotypes in the most popular 10 haplotypes. This evidence indicates that Japanese and Korean have the common genetic back ground.