A growing body of evidence from experimental studies that shows the essential role that magnesium exerts on glucose metabolism has been developed in last years, strongly suggesting that magnesium could plays an important roles in the reduction of the risk of developing type 2 diabetes. In the clinical setting, large epidemiological studies show that low dietary magnesium intake is associated with the increased risk of developing type 2 diabetes; however, results from randomized controlled clinical trials that have evaluated the beneficial effects of magnesium supplementation on glucose metabolism and insulin sensitivity are controversial. In this article we searched (in the electronic databases of Medline, Embase, and the Cochrane Controlled Trials Register up to June 2011) the evidence derived from epidemiological studies and clinical trials, about the relationship between magnesium and type 2 diabetes. The body of evidence from epidemiological studies consistently shows a strong inverse relationship between dietary magnesium intake and the risk of developing T2D; however, results from clinical trials are scarce and controversial.