Lymphangiograms of canine cardiac and pulmonary efferent mediastinal lymphatics were made by cannulation and injection of Ethiodol®. Injections were made singly and serially. The mediastinal lymphatics and lymph nodes, which constitute the pathways of drainage of the heart and lungs, were delineated from the point of cannulation to the right and left inferior cervical region where the right lymphatic duct and thoracic duct are located. Lymphangiography reveals that the lymphatics which drain the heart and lungs may join to form common mediastinal lymphatic channels. Interconnections between mediastinal channels were demonstrated. The lymphatics terminated in the region of both the right lymphatic duct and thoracic duct in every subject. The so-called “cardiac node of Drinker” is usually a group of pretracheal nodes rather than a single node. The pretracheal nodes and those more cephalad receive drainage of lymph from both the heart and lungs. These studies suggest that lymph collected by cannulation of a “cardiac” lymphatic adjacent to the “cardiac node” will contain pulmonary as well as cardiac lymph. Thus the high flows reported by many investigators for “cardiac” lymph probably indicates that pulmonary lymph is mixed with cardiac lymph, and that the experimental data should be interpreted with this in mind.