Rituximab (RTX) is a chimeric murine/human monoclonal antibody directed against the CD20 surface antigen of B cells. RTX has been for the treatment of non-Hodikin lymphoma. Recently, RTX was shown to be effective in treating patients with myasthenia gravis (MG) who did not show improvement with other immunomodulation treatments. However, the evidence of its efficacy is mostly limited to a few case series or open-label trials. At the present stage, RTX may be permitted to be used in patients who understand the risk of its side effects and provide consent for its use in treatment. In future, it will be necessary to establish an effective and safe medication protocol of RTX in Japan.