Type 2 diabetes is 8 to 10 times more common than type 1 diabetes, but no single large trial has established that improved glycemic control can prevent complications in type 2 diabetes. We have reviewed the results of the existing epidemiologic and clinical trial studies and have arrived at the following conclusions: (1) Strong evidence exists that improved glycemic control is effective at lessening the risks of retinopathy, neuropathy, and nephropathy in type 2 diabetes. (2) The evidence about the effect on coronary heart disease is limited and equivocal. (3) The hypoglycemic risk from improved glycemic control is significantly less in type 2 diabetes than in type 1, and weight gain seems to be modest. In conclusion, although glycemic goals should be individualized based on several clinical factors, most patients with type 2 diabetes would probably benefit from glucose lowering to a hemoglobin A1c level between 7% and 8%.