Abstract: There were 23 cases of NHL which had been done the two biopsies in had happened the histological transformation. The interval time between the two biopsies was 12- 54 months.The clinical charater was the local lymph node enlargment was then developed into the lymph node enlargment all over the body. Clinical stage I up II-IV. In histological transformation 3 cases of the follicular type lymphoma hacl been transformed into the diffuse type lymphoma.3 cases of the small cleaved cell type into the deaved-noncleaved cell type. 1 case of the deaved-noncleaved cell type into the large nondeaved cell type. 1 case of the B small lymphocytic lymphoma into the immunoblastic lyrrr phoma The results indicated that NHL could happen the histological transformation in the development of the disease from the lower grade milignant lymphoma into high grade milignant lymphoma.