Zevalin (ibritumomab tiuxetan; IDEC Pharmaceuticals Corporation, San Diego, CA, USA) was approved by the United States Food and Drug Administration on February 19, 2002, following 9 years of clinical development. Six clinical studies supported the Zevalin Biologics License Application. The Zevalin regimen is indicated for the treatment of patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma (NHL), and for those with follicular NHL refractory to Rituxan (rituximab, MabThera; IDEC Pharmaceuticals Corporation, San Diego, CA and Genentech, South San Francisco, CA). In the year following FDA approval, approximately 1300 patients were treated in clinical trials or with the commercially available product.