Chronic venous insufficiency affects to differing extents half of the French population. The most advanced forms, with skin changes (CEAP clinical classes C4-5-6) affect 5% of the population and are those most often indicated for spa treatment. A venous condition is recognized as justifying spa therapy by 12 spa resorts in France. However, no specific or global benefit has been clearly scientifically shown for such therapy. One methodologically sound study (Carpentier 2009) demonstrated a benefit of spa therapy using a non-clinical intermediate endpoint (severity of skin changes). No study has shown efficacy of spa therapy in the primary and secondary prevention of the major and most common complication of advanced chronic venous insufficiency: leg ulcers.