The Ann Arbor staging classification has proved to be valuable for Hodgkin's disease. When proposed in 1971 it was thought that it could also be applied to the non-Hodgkin's lymphomas. The diversity of the non-Hodgkin's groups, the continued evolution of histopathologic classifications, and the great frequency of advanced disease in the lymphocytic subgroups make the Ann Arbor classification of only limited value for the non-Hodgkin's lymphomas.