Some types of non-Hodgkin lymphomas cannot be treated by contemporary preparations. After repeated relapses and chemotherapy moreover damage of bone marrow occurs and further intense cytostatic treatment is not possible. Monoclonal antibodies against structures on tumour cells are an interesting alternative of cytostatic treatment. In 2000 the authors administered anti CD20 monoclonal antibody (rituximab, Mabthera Roche), 375 mg/m2, on the 1st, 8th, 15th and 22nd day i.v. to a total of 24 patients with relapsing non-Hodgkin lymphoma. In five patients the relapse developed after high dosage chemotherapy and autologous transplantation of peripheral stem cells. Treatment was well tolerated with minimal side-effects. Favourable therapeutic results were recorded in patients with follicular lymphoma (70% of the therapeutic responses), small lymphocyte lymphomas (64% of therapeutic responses) and in patients with a relapse after autologous transplantations (80% of therapeutic responses). Anti CD20 monoclonal antibody is a new effective alternative of cytostatic treatment. Its position in the therapeutic strategy in patients with non-Hodgkin lymphoma awaits elaboration.