All published studies that evaluated the association between rs5219 of KCNJ11 (p.E23K) and T2DM or NIDDM were collected through a PubMed search of studies published before June 2014 using the search terms “KCNJ11”, “polymorphism”, “T2DM”, and “rs5219” in different combinations. This evidence concerns the gene KCNJ11 and type 2 diabetes mellitus.