Rituximab, a chimeric anti-CD20 monoclonal antibody, has become a part of standard treatment of B-cell non-Hodgkin lymphoma in the last several years. Depleting CD20+ cells by various mechanisms, it is active as a single agent and particularly when combined with chemotherapy. It is effective in "in vivo" elimination of neoplastic cells from the hematopoetic stem cell transplant. Side-effects are mostly infusion related, mild to moderate, mediated by cytokine release. Because of different mechanisms of action, adding rituximab to chemotherapy does not cause additional toxicity. Combination of rituximab and chemotherapy improves response rates in indolent lymphomas and survival in aggressive lymphomas.