Lymphedema is a chronic disease associated with a congenital or acquired disorder of the lymphatic vessels or lymph nodes. Untreated lymphedema can lead to complications and disability. Clinical Lymphology deals not only with lymphedema of the extremities but also of the head, the genitals and the internal organs (lymphostatic enteropathy, chylaskos, chylothorax, chylopericard etc). Symptoms of this disorder are often misdiagnosed or not recognized. Ignorance and trivialization of lymphedema causes insufficient treatment, which then is not carried out to the extent as it is possible today by scientific findings. Even today delayed or not optimal treatment causes a long ordeal for many patients.The fact that lymphedema for those affected is a major psychological and social burden, which is limiting the quality of life, has also often been unregarded. The knowledge of anatomy, physiology and pathophysiology as well as the knowledge of causes are necessary for diagnosis, so that early treatment can be initiated.