Diabetic nephropathy represents the most important microvascular complication in long-term diabetes mellitus because chronic renal insufficiency is further aggravated by increased cardiovascular morbidity and mortality in diabetic patients. Although early intensive insulin therapy has led to a significant reduction of incidence and prevalence of end-stage renal failure over the last decades in juvenile type 1 diabetes mellitus, the total number of type 2 diabetic patients with chronic renal insufficiency is dramatically increasing due to the improved life expectancy of the general population and the more effective medical treatment of macrovascular complications such as arterial hypertension, coronary artery disease, and peripheral arterial occlusive disease. Apart from the personal burden for each individual the frightening epidemiologic dimension of diabetic nephropathy represents an outstanding challenge for our social systems.