Rituximab is an anti-CD20 antibody used to deplete B lymphocytes in lymphoma and autoimmune disease. Case reports in the literature describe patients who paradoxically develop autoimmune disease in response to rituximab therapy. We review the reports of autoimmune pathology in response to rituximab treatment and the proposed mechanisms of this reaction. These autoimmune diseases manifest in various organ systems, most frequently the skin and lungs, and involve distinct mechanisms of pathogenesis mediated by potential alterations in B and T lymphocytes, innate immune system, and specific environmental factors. Those clinicians utilizing rituximab should be aware of this unusual phenomenon.