The involvement of the lymphatic drainage in patients with postthrombotic syndrome can be verified by (quantitative) isotopic lymphography (99m Tc labelled microcolloids) and by indirect lymphography (water-soluble contrast medium Iotrolan). Both methods point to an augmented praefascial lymph-transport. In the region of lipodermatosclerotic skin changes dermal backflow can be explained by a local damage of peripheral skin-lymphatics ("localized lymphoedema"). No working lymphatics can be found in the border of ulcers. As could be demonstrated by intramuscular injection of the radioactive tracer subfascial lymphtransport is decreased not only in the postthrombotic stage but already in the acute phase of a deep vein thrombosis. The alterations of the lymph-drainage in a postthrombotic syndrome may have some pathophysiological importance for the development of the tissue changes and may also explain some clinical signs.