To determine the possible participation of genetic factors in the pathogenesis of Takayasu's arteritis and to investigate an association between HLA antigens and the disease, we performed HLA typing in twenty two patients confirmed by clinical findings and aortography, and in fifty normal Koreans as controls. HLA-A, B,C and DR antigens were tested by standard microlymphocytotoxicity method with HLA antisera, which were supplied by UCLA Tissue Typing Laboratory. The results were as follows: 1) Frequent antigens of HLA-A locus in patients were A 2(54.5%), Aw 33(31.8%), Aw 24(27.2%) and A26(13.6%) in decreasing order, and Aw 33 was more frequent in patients than in normal controls(18.0%)(relative risk: 2.1). 2) Frequent antigens of HLA-B locus in patients were Bw61(31.8%), Bw44(31.8%), Bw62(22.7%) and Bw52(13.6%) in decreasing order, and Bw61 was more frequent in patients than in normal controls(10%)(relative risk : 4.2). 3) Frequent antigens of HLA-C locus in patients were Cw3(54.5%), Cw6(50.0%) and Cw1(22.7%) in decreasing order. 4) Frequent antigens of HLA-DR locus in patients were DR6Y(36.4%), DR2(31.8%), DRw9(27.2%), DR4(27.2%) and DR28(22.7%) in decreasinng order. In MT system MT 3 was more frequent in patients(54.5%) than in normal controls(31.6%)(relative risk : 2. 6). However, the difference of HLA antigen frequencies between patients and normal controls was not statistically significant, and the association of specific HLA antigens with Takayasu's arteritis requires further studies to be confirmed.