Genome-wide association studies (GWAS) provide important insights into type 2 diabetes (T2D) pathogenesis. The common variant GWAS approach enables capture of disease risk-associated sequence variation on a previously unachievable scale, implicating roughly 70 genomic regions in T2D predisposition. Data gathered from a variety of approaches, including GWAS studies in diverse ethnic groups, indicate that a substantial proportion of the heritable component of T2D risk is attributable to causal common variants of small effect that are shared across populations. Whilst the 70 common variant signals detected at genome-wide significance account for only 5-10% of overall variation in disease predisposition, their discovery infers much about T2D pathophysiology. Genes mapping to T2D susceptibility loci are enriched for transcription factors and cell cycle regulators, yet only partially overlap pathways influencing physiological variation in glycaemic traits. Most affect insulin secretion, and some influence birthweight, linking intrauterine growth to adult metabolic disease. Challenges in identifying the causal variants and mediating transcripts behind common variant GWAS signals remain. However, the increasing sophistication with which non-coding association signals can be mapped onto tissue-specific regulatory annotations, and the growing power of efforts to detect rare variant signals in coding sequence, are providing new opportunities to link common variant GWAS signals to biology.Type 2 diabetes (T2D) is a global health burden. It accounts for 6.8% of deaths worldwide [1], and will rise in prevalence at a rate exceeding that of adult population growth [2]. Despite an influence of obesity [3] and urbanisation [4], a wealth of data supports a substantial inherited contribution to this disorder. For example, first-degree relatives of those with T2D are at increased risk [5], and the concordance for diabetes in monozygotic twins is twice that in dizygotic pairs [6].At the same time, the complex interplay between pancreatic insulin secretory failure and peripheral insulin resistance which characterises T2D implies both phenotypic and genetic heterogeneity [7]. Aetiological complexity, along with inadequate understanding of the processes involved in glucose homeostasis, frustrated early ef-