Conjugated antibodies have been in clinical trials for over 30 years. Immunotoxins, chemotherapy conjugates and radioimmunotherapies have been evaluated. Zevalin, the first conjugated antibody for the treatment of non-hodgkin's lymphoma (NHL) (and the first radioimmunotherapeutic for cancer) was approved by the US FDA on 19 February 2002 (approval is pending in the EEC). Zevalin (90Yttrium ibritumomab tiuxetan) has been in clinical trials since 1992. Several studies have been conducted including a randomized Phase III trial where it showed superiority to rituximab in overall response rate and in complete response rate. The current indications are: low-grade or follicular lymphoma refractory to rituximab, and relapsed or refractory, low-grade, follicular or transformed lymphoma. Additional studies have been initiated to further define the role of this new therapy in the treatment of patients with B-cell non-hodgkin's lymphoma.