Rituximab is a chimeric monoclonal antibody directed against CD20 antigen. This molecule is expressed only on the surface of B lymphocytes, it is present neither on precursor cells nor on plasma cells. CD20 antigen is not internalized nor shed. Infusion of rituximab evokes rapid B-cell depletion. It is caused mainly due to complement activation and antibody-dependent cellular cytotoxicity. Furthermore, rituximab acts synergistically with standard chemotherapy, sensitizing cells to apoptosis, via inhibition of the expression of Bcl-2 protein. Rituximab has been registered for the treatment of non-Hodgkin’s lym- phoma, but its indications are still expanding. Currently it is also approved in the treatment of rheumatoid arthritis, however it is also used in other autoimmune disease as well as in transplantology. On the basis of success of rituximab new drugs are being made against CD20 antigen. These are, among others: monoc- lonal antibodies conjugated with radioisotopes, completely human monoclonal antibodies or small pepti- des (mimotops), which are designed to induce the response of the immune system against CD20 antigen.