The incidence of Thromboangiitis Obliterans in brothers and the high prevalence in some ethnic groups have led us to investigate the histocompatibility HLA—A, B and DR antigens of 46 Buerger's disease patients. The main result indicates a marked decreased frequency of the B12 antigen: 2.2% vs 28% in controls. Our study suggests that Buerger's disease is, on the basis of HLA antigens, a distinct immunogenetic entity and not a particular form of arteriosclerosis. Moreover, this disorder may represent a clue to the existence of resistance genes linked to HLA.