The relationship between glycemic control and diabetic complications remains unclear. Epidemiological studies reveal that approximately 25% of diabetic individuals do not develop complications, irrespective of degree of glycemic control. Studies of genetic factors, including HLA type, capillary basement membrane thickness, genetic predisposition to hypertension, and familial clustering of diabetic complications, suggest that there is a genetic component to developing the complications of diabetes. On the other hand, clinical trials have demonstrated that the progression of early, mild background retinopathy, microalbuminuria, and parameters of nervous system function are stabilized with improved glycemic control. Other metabolic parameters, such as serum lipoprotein levels, are significantly improved with near normoglycemia. No studies to date have evaluated the effect of blood glucose control on the prevention of diabetic complications. The degree of glycemic control required to impact on diabetic complications is unknown. In addition, achieving near normoglycemia carries increased risk for severe hypoglycemia and weight gain. Further study is needed to determine the long-term benefits of blood glucose control and to weigh that against the risks of improving glycemic control. Further investigation also is needed to address the probable interrelationship of genetic factors and glycemic control on the development of diabetic complications.