Background: Rituximab is a human-mouse chimeric IgG1 monoclonal antibody directed against antigen CD-20, transmembrane phosphoprotein on B cells. This drug induce depletion of B cells and subsequent reduction in antibody production. Recently there were cases of severe AChR-antibody positive and MuSK-positive myasthenia gravis (MG) successfully treated with rituximab. Case report: Forty-three-year-old women with refractory MG with predominantly generalised weakness in extremities, bulbar symptoms and dyspnea, who presented for the first time in 1992. Thymectomy was perform in 1997. During 15 years of therapy patient had one crise in 1997 and one in 1999. In 2007, she had five hospital admission. She did not respond adequately to acetylcholinesterase inhibitors, thymectomy, repeat plasma exchange and conventional immunosuppressive therapy such as azathioprine, cyclophosphamide and prednisone. For this reason rituximab (MabThera®, Roche) therapy was added. Rituximab was administered at a dose of 375 mg/m2 intravenously according to a protocol every 7 days for 4 weeks. She received also prednisone at a dose of 20 mg and pyridostigmine 180 mg per day all the time. Within 4 weeks therapy she showed maintained clinical improvement. Dyspnea and bulbar symptoms were disappearanced and walking distances was longer. We did not observe serious adverse events, only after first infusion transient oedema of mucosa nasal and oral cavity with concurrent pruritus and after second infusion transient myalgia, chills and subfebrile body temperature were found. Conclusions: In this case use of rituximab leading to significant clinical improvement in refractory myasthenia gravis. The therapy was well tolerated and any serious adverse events were registered.