Recent linkage and association studies provide evidence for thyroglobulin (Tg) being an autoimmune thyroid disease (AITD) susceptibility gene. The Tg locus has been reported to be linked with AITD in two independent studies, and further analysis demonstrated that markers within the Tg gene were associated with AITD. Furthermore, missense single-nucleotide polymorphisms (SNPs) in the Tg gene were shown to be associated with autoimmune thyroiditis in both mice and humans. If Tg is confirmed as a susceptibility gene for AITD, it could provide a novel therapeutic target.