The distinctive clinical features of malignant lymphoma among malignant tumors are as follow : Firstly histopathological classification, staging classification, staging system, and treatment policy of malignant lymphoma, especially in non-Hodgkin's lymphoma, are still in controversy. Secondly its therapy has been done mainly with radiotherapy and/or chemotherapy. Indication of surgery is limited, except gastrointestinal cases in stage I. Thirdly staging procedures are very important in deciding its stage and treatment policy, because insufficient examinations cause underestimate of disease and improper treatment. Considering these problems, this paper reviews the current discussions on the definition, staging systems, treatment policies and side effects in the literatures. Staging system, treatment policiy and its results at Shinshu University Hospital are discussed in comparison to those of other institutes.