In the diagnostics of the malignant lymphomas is to be differed between the proper diagnosing, i. e. the morphological confirmation of the disease and the enlarged diagnostics which, after ascertainment of the histologicopathological findings and prior to the beginning of a therapy is necessary for the statement of the size of the spreading of the disease (classification of stages) as well as for the inclusion in group A or B and for the registration of the most different signs of activity. Swellings of the lumph nodes in adults should be clarified morphologically after three weeks, since only on this way an early diagnostics is guaranteed. In an unclear fever an abdominal lymphogranulomatosis is to be excluded. The explorative laparotomy and splenectomy is - if possible - to be performed before the beginning of a treatment. When pronounced signs of activity are present, however, a cytostatic treatment should precede this operation in order to decrease the risik of the operation. The classification in stages with exclusively clinical examination methods at present comprises a vast number, which in all stages must always be performed as an interdisciplinary task in a haematologico-oncological centre under control of an internist. The classification after Kiel of the non-Hodgkin-lymphomas does not only demand the knowledge of the nomenclature, but also the evaluation by the internist in order to perform the optimum therapy in these patients.