Rituximab was the first monoclonal antibody to have been registered for the treatment of B-cell lymphomas. Randomized studies have demonstrated its activity in follicular lymphoma, mantle-cell lymphoma, and diffuse large B-cell lymphoma in untreated or relapsing patients. Because of its high activity and low toxicity ratio, rituximab has transformed the outcome of patients with B-cell lymphoma. A combination of rituximab plus chemotherapy, R-CHOP has the highest efficacy ever described with any chemotherapy in diffuse large B-cell lymphoma and follicular lymphoma. The role of radio-labelled antibodies is still to be defined.