Graves' disease is a thyroid autoimmune disorder associated with specific human lymphocyte antigen (HLA) alleles, characterized by an unpredictable long-term course. To investigate possible relations between HLA phenotype and outcome of the disease, the authors typed for HLA antigens in 105 patients with Graves' disease with different course of disease. All patients were treated with antithyroid drugs for at least 12 months; 29 patients had stable remission 24 or more months after withdrawal of treatment; 76 patients had persistent disease—66 unremitting/relapsing hyperthyroidism, 10 stable hypothyroidism—36 or more months after onset of disease. The following findings emerged from this study: 1) HLA B8 and DR3 were increased significantly in Graves' patients versus 6,682 control subjects from the same geographic area (23.80% vs 12.01%, odds ratio [OR] 1.98, and 31.43% vs 18.00%, OR 1.75, respectively); the antigen combinations B8-DR3, B8-Cw7-DR3, and A1-B8-Cw7-DR3 were significantly more frequent in Graves' patients vs control subjects; in addition, these combinations were present exclusively in patients with persistent disease (B8-DR3 28.95%, OR 7.14, B8-Cw7-DR3 27.63%, OR 11.24, and A1-B8-Cw7-DR3 18.42%, OR 11.29). These data provide evidence that not only susceptibility to Graves' disease, but also persistent activity of the autoimmune process, producing either hyperthyroidism or stable hypothyroidism, is associated with specific HLA antigen phenotypes.