The rituximab antibody is a genetically engineered chimeric murine/human monoclonal antibody directed against the CD20 antigen found on the surface of normal and malignant B lymphocytes. Rituximab is indicated for the treatment of patients with relapsed or refractory, low-grade or follicular, CD20-positive, B-cell non-Hodgkin lymphoma. Rituximab is also commonly used to treat chronic lymphocytic leukemia, Waldenstrom's macroglobulinemia, and immune or idiopathic thrombocytopenic purpura (ITP). Rituximab is an effective treatment for primary cutaneous B-cell lymphoma and other cutaneous lymphomas. Rituximab is an effective treatment for mixed cryoglobulinemia. Rituximab is a promising treatment for systemic lupus erythematosus, dermatomyositis, pemphigus, vasculitis, and a variety of hematologic diseases. Black-box warnings on rituximab include fatal infusion reactions, tumor lysis syndrome, and severe mucocutaneous reactions. A variety of cardiac, pulmonary, renal, and hematologic side effects can occur. It commonly causes mild cutaneous side effect and rarely has caused paraneoplastic pemphigus, Stevens-Johnson syndrome, lichenoid dermatitis, vesiculobullous dermatitis, and toxic epidermal necrolysis.