The diseases associated with HLA in Japanese, for which more than two laboratories have confirmed the association, were listed. The association first reported by Japanese researchers and confirmed by researchers of other countries like the association of narcolepsy and HLA-DR2 was stressed. There are some diseases like Takayasu' disease, the association of which was found and confirmed only in Japanese. On the other hand, there are many diseases, the association of which has been reported in the races other than Japanese. Extremely close association of HLA-B27 and ankylosing spondilitis has been observed in Japanese as well as the other races, but as to the other B27 related diseases the association is not clear in Japanese. HLA antigens associated with type I diabetes mellitus in Japanese are HLA-Bw54, DR4.1 and DwYT, which are quite different from the ones in Caucasians. The haplotype comparable to Caucasian A1-B8-DR3-Dw3 has not been found in Japanese. The mechanisms of the associations are still remain to be resolved. Some influential hypotheses such as the presence of Ir and Is genes linked to HLA loci and a single mutation were discussed.