The first antibody approved for the treatment of cancer, rituximab (Rituxan/MabThera), underwent clinical development between 1993 and 1996. It fulfilled predictions dating back to the early 1900s regarding the therapeutic effect of antibodies and sparked a renewed interest in this area of research. Rituximab was approved, in the USA in 1997 and in Europe in 1998, for the treatment of patients with non-Hodgkin's lymphoma. Since then, hundreds of thousands of patients have been treated with rituximab. In 2002, rituximab became the number one anticancer drug worldwide. During its first decade of use (1993-2003), rituximab has had an important impact on treatment strategies for lymphoma and other hematologic malignancies. During the 5 years following approval, its applications expanded beyond non-Hodgkin's lymphoma to a variety of malignant and non-malignant B-cell disorders. Also, as a result of its early clinical trials, initiatives came about that eventually led to the development of the new international response criteria for non-Hodgkin's lymphoma. Rituximab has been characterized as the most important therapeutic development of the decade.