The distribution of class I HLA antigens (HLA-A, B) were determined in 50 patients of Aortoarteritis in an Indian population. This included 29 females and 21 males. The difference in antigen frequency was observed between patients and controls with reference to HLA-A19, B5 and B21 antigens. A decreased frequency of HLA-A19 was observed in the patients as compared to controls (14% vs 33.25%, X2 = 6.81, P less than 0.025). Of the B locus antigens, an increased frequency of HLA B5 was observed in the patients as compared to controls (48% vs 29.5%, X2 = 6.2, P less than 0.025). HLA-B21 was also increased in the patients as compared to the controls (18% vs 6.5%, X2 = 6.67, P less than 0.025). These data suggest the involvement of genetic factor (s) in the aetiopathogenesis of this disease. Further, the observations indicate that HLA-B5 and B21 may be associated with Aortoarteritis.