The post-therapeutical secondary arm lymphedema is the most frequent complication after a curatively treated cancer of mamma. For the diagnosis and therapy the knowledge of physiology and pathophysiology of lymphedema and of specific anatomy are necessary. The diagnosis facilities are essentially limited to a basic diagnosis (anamnesis, inspection, palpation, sonography, functional-diagnosis). Specific apparative diagnostics like lab, sonography, CT, MRI and PTE have to be applied especially at an early stage of the secondary arm lymphedema for the differential diagnosis between the secondary malign and secondary benign arm lymphedema. Specific apparative examinations like lymphscintigraphy and lymphography are limited and solely indicated for special questions. As a therapy possibility of the secondary arm-lymph edema, a conservative therapy, that is, the complex two-stage-decongestive physiotherapy (CDP) is recommended as first choice. Surgical therapies such as autologous lympho-lymphostatic anastomoses and lymphovenous anastomoses are only recommended in selected individual cases. The secondary malignant arm lymphedema must be primarily treated oncologically; lymphological therapy measures have to be postponed. Diagnosis and therapy are limited through lymphological incompetence and insufficient patient compliance. In this respect the provision of financial resources through National Health policy ist regarded as utterly important.