The measurement of capillary permeability in chronic venous insufficiency (CVI) requires techniques able to modify local microcirculatory hemodynamics and therefore the results. As for instance, venous occlusion in the Landis test or occlusive plethysmography. We are presenting a selective method which visualizes and quantifies capillary permeability without modifying the hemodynamics. A skin area on the lower extremity is observed on a microscope with blue filters. This optical device is linked with a camera transmitting information to a TV monitor and a video cassette recording system. When focusing is done, the patient's brachial vein is injected with an IV bolus of 1 ml if sodium fluorescein (Na flu). This dye diffuses rapidly from the intra toward the extra-capillary compartment. A densitometer connected to a graph measures the capillary permeability selected dynamics. The capillary permeability to Na flu is evaluated qualitatively on the TV screen (pericapillary halo), and quantitatively by the densitometric curve. In practice, this technique is advocated in the physiopathological study of any edema, especially in early CVI.