The post-thrombotic syndrome (C3a-6a/s Es +/- p Ad +/- s +/- p. Pr/o) deserves the special attention of specialized physicians for many reasons : it must be prevented after any deep vein thrombosis it must be taken care of early in order to prevent ulceration it can benefit from a surgical restauration. We present in this article instrumental criteria and a diagnostic algorithm allowing to refine the management.