There is a physiological necessity for the existence of lymphaticovenous communications in points other than the terminal entry of the lymphatic trunks into the superior caval system. These communications are frequently seen, as well in clinical practice as in experimentation, when there is an obstacle to the downstream lymphatic flow, but their exact nature cannot be determined. We have been able to demonstrate on the rat that such communications are established within the lymph nodes. We shall discuss the physiological importance of our findings together with a review of the literature and consider their clinical and therapeutic consequences.