The prognosis of non small cell lung cancer (NSCLC) invading the diaphragm is poor, probably due to the richness of the lymphatic drainage of the diaphragm. The aim of this study was to determine mediastinal lymphatic efferents from the diaphragm. The diaphragms of 20 adult cadavers (77-104 years) were injected with a dye (modified Gerota's medium) to permit the lymph vessels to be catheterised and then dissected. Each stage of the dissection was described and photographed: 23 injections on the right and 25 on the left. Diaphragmatic lymph vessels passed to one of three lymph centres: posterior (paraaortic nodes, n = 16), anterior (juxtasternal nodes, n = 16) and mediastinal (visceral nodes, n = 16). From these lymph centres arose ascending lymph pathways: posteriorly to the thoracic duct (8/16), anteriorly along the internal thoracic vessels (10/16) and in the mediastinum to the peritracheobronchial nodes (6/10). Lymphatics from the diaphragm are abundant and drain towards mediastinal node lymph centres connecting to the blood stream via the thoracic duct. These lymph pathways are common with those of the pulmonary segments. Poor prognosis of NSCLC invading the diaphragm may be explained by the common lymphatic drainage of both the lung and diaphragm.