Takayasu's arteritis, with a strong predilection for women and particular geographic areas, has revealed significant association with human lymphocyte antigens (HLA) specificities. In the present study, the authors investigated for the first time the association of Takayasu's arteritis and HLA at the genomic level. By use of a restriction endonuclease Taq-I and a DQA cDNA probe, HLA-D region restriction fragment length polymorphism was examined in 32 Japanese patients. It was revealed that 65.6% of the patients shared a 6.6 kb fragment, although this fragment was found in 35.3% of the healthy Japanese (Chi square: 6.07, p less than 0.02). This finding suggest that HLA-D region gene variations determine susceptibility to Takayasu's arteritis.