In juvenile diabetes there is a renal hypertrophy: glomerular volume and capillary lumen of the individual glomeruli are about twice the size of healthy ones. The hypertrophy is associated with a hyperfunction (increased glomerular filtration and tubular reabsorption). If the diabetes is strictly controlled these changes may regress, which suggests a metabolically induced hypertrophy. Long-standing diabetes is characterized by a phase of intermittent proteinuria which gradually becomes permanent. Diabetic angiopathy is the result of many years of abnormal metabolism, presumably with involvement of the growth hormone and glucose. Whereas microangiopathy is considered specific for diabetes, it is still a matter for discussion whether a diabetic macroangiopathy exists. The results of numerous investigations suggest that it does.