The lymphatic system plays an important role in human circulation and organ perfusion homeostasis (1). Disorders of the pulmonary lymphatic system occur in a variety of clinical settings (ranging from trauma to cancer) and may lead to serious pulmonary disease (Figure 1A). In addition, congenital errors of lymphatic development can lead to primary pulmonary lymphatic disorders (lymphangiomas, lymphangiectasis, lymphangiomatosis, and lymphatic dysplasia syndrome)(2–8). Because of their scarcity, these latter conditions are often misdiagnosed (Figure 1B) and their management is difficult. Research on thoracic lymphatic disorders has been hampered by a confusing and inconsistent use of terminology. Their origins and pathogenesis are currently unknown. Future advances in our understanding of vasculogenesis may provide clues about the relation between abnormal embryogenesis and the development of lymphatic disease.