The spa therapy techniques used in the context of venous insufficiency have well-defined physiopathic targets and the hemodynamic and microcirculatory effects of some of them have been demonstrated. The high degree of satisfaction of patients taking the waters annually for venous conditions indirectly testifies to their enhanced well-being. Among venous indications, the prevention of post-thrombotic syndrome is one of the best recognized by the medical profession.Nevertheless, there has been no real validation of this indication with an acceptable methodology that meets the canons of evidence based medicine.