Metformin, a dimethylbiguanide, was first synthesized in 1929 and was shown to be a potent hypoglycemic agent. It was rediscovered in 1957 and was widely used in Europe to treat obese type II patients. Metformin resurfaced in the 1980s and was shown to increase insulin sensitivity; this has led to its introduction to clinical practice in the United States for the first time. The small risk of lactic acidosis is now well documented and appropriate therapeutic guidelines have been established. Metformin is a sage and effective drug for management of non-insulin-dependent diabetes mellitus.