Histologic criteria for the diagnosis of Hodgkin's disease are being modified, primarily as a result of phenotypic analysis. It seems likely that non-Hodgkin's lymphomas have been diagnosed as mixed-cellularity and lymphocytic-depletion Hodgkin's disease on the basis of previously accepted histologic criteria. As a result, phenotypic studies are indicated in all examples of lymphocytic-depletion Hodgkin's disease and in those cases of mixed-cellularity Hodgkin's disease in which the histologic findings are unusual. The effects of genotypic analysis on histologic criteria remain to be elucidated.