Biopsies of 82 patients diagnosed as having Hodgkin's disease were reviewed. Seventeen were reclassified histologically as non-Hodgkin's lymphoma or reactive lymphoid hyperplasia. A substantial number of cases of Hodgkin's disease were negative when stained with Leu M1. Staining for Leu M1 was not found in the cases of non-Hodgkin's lymphoma or reactive lymphoid hyperplasia. With the exception of the lymphocyte predominant nodular subtype of Hodgkin's disease, epithelial membrane antigen staining was seen in a few cases of Hodgkin's disease and non-Hodgkin's lymphomas. This was not a useful discriminating feature.