[en] BACKGROUND: The existence of intratissular lymphaticovenous anastomoses has often been suggested, but it has never been demonstrated. This study aims at demonstrating the presence of such anastomoses. METHODS AND RESULTS: The free flap model was used to investigate the drainage of radiolabeled colloid particles whose size prevents direct passage to the blood vessels. The tracer was injected into the muscle or the skin during the surgical procedure. Blood samples were sequentially drawn from the venous pedicle over the 30 minutes that followed the tracer injection. The blood samples were counted using a gamma well-counter. In all 14 patients, the venous blood radioactivity steadily increased over time. Radiochemical analyses performed on the blood samples demonstrated that the radioactivity is related to the labeled colloids and not to free pertechnetate. Planar imaging performed 24 hours after the surgical procedure showed a significant liver uptake, and no accumulation in the area of normal lymphatic relays. CONCLUSIONS: As, in the free flap model, there is no lymphatic drainage through the classical pathways whatsoever, and since the size of the radiolabeled particles prevents them from directly entering the blood stream, the results strongly suggest the presence of functional intratissular lymphovenous anastomoses.