AbstractVenous ulceration is caused by the disorganization of the microcirculation that is induced by prolonged venous hypertension. The most common cause of calf pump inefficiency that permits superficial venous hypertension during exercise is deep vein thrombosis. Venous hypertension causes venular dilatation and an increased capillary permeability. Fibrin is deposited around the capillaries and not removed because of a vein wall deficiency of the fibrinolytic activator. The fibrin acts as a diffusion barrier and the overlying dermis becomes anoxic. Any minor trauma then causes an ulcer. Ulcers can be cured by restoring calf pump function to normal. Postthrombotic skin changes caused by irreparable calf pump damage can be reversed by the regular use of elastic compression and the pharmacological long‐term enhancement of fibrinolysis.