Functional alterations of the microvasculature are studied in this project. In particular, the permeability of the renal peritubular capillaries to albumin and that of other capillaries to small molecules are investigated in animals that were made insulin deficient diabetic by injection of streptozotocin. These experiments are carried out by using measuring techniques which are suitable to detect early changes. These experiments are conducted with a view towards determining potential variables which can influence the rate of development and severity of microvascular disease in experimental diabetes.