The P12A polymorphism in the gene encoding the peroxisome proliferator-activated receptor-g (PPARG) [7], the E23K polymorphism in the gene encoding the islet ATP-dependent potassium channel Kir6.2 (ABCC8-KCNJ11) [8-10] and common variants in the gene encoding the transcription factor 7-like 2 gene (TCF7L2) [11,12] were all found using well-powered association mapping, and all have been reproducibly associated with diabetes in diverse samples at highly significant p-values. Here, TCF7L2 is linked to diabetes mellitus.