Graves' disease is a complex autoimmune disorder in which several genetic susceptibility loci and environmental factors are likely to contribute to the development of disease. HLA and the CTLA-4 gene region have been established as susceptibility loci, although the magnitude of their contributions seems to vary between data sets and geographic populations. Genome-wide searches are beginning to identify new loci, including GD-1, GD-2, and GD-3, although these loci have only been found in one data set. Additional loci are likely to be identified via a combination of genome-wide linkage analysis and allelic association analysis of candidate genes.