Despite numerous candidate gene and linkage studies, the field of type 2 diabetes (T2D) genetics had until recently succeeded in identifying few genuine disease-susceptibility loci. The advent of genome-wide association (GWA) scans has transformed the situation, leading to an expansion in the number of established, robustly replicating T2D loci to almost 20. These novel findings offer unique insights into the pathogenesis of T2D and in the main point toward the etiologic importance of disorders of beta-cell development and function. All associated variants have common allele frequencies in the discovery populations, and exert modest to small effects on the risk of disease, characteristics that limit their prognostic and diagnostic potential. However, ongoing studies focusing on the role of copy number variation and targeting low-frequency polymorphisms should identify additional T2D susceptibility loci, some of which may have larger effect sizes and offer better individual prediction of disease risk.