In this Archives, Armitage et al (p 445) provide additional evidence that non-Hodgkin's lymphomas occur with increased frequency in patients previously treated for Hodgkin's disease. Twenty-nine cases have been reported in the literature. It is now apparent that these cases represent the development of a second malignant neoplasm distinct from Hodgkin's disease. Although lymphocyte-depleted Hodgkin's disease can occasionally be difficult to separate from diffuse non-Hodgkin's lymphoma, none of the patients were seen with that form of Hodgkin's disease. Therefore, it is extremely unlikely that these cases represent a subsequent different diagnosis for the same initial pathologic process. The assumption that two different diseases are involved is also supported by the finding of Armitage et al that the malignant cells in these non-Hodgkin's lymphomas may have markers of either T, B, or null lymphocytes. Although the exact origin of the malignant Reed-Sternberg cells in Hodgkin's disease remains controversial, the lymphocytic infiltrate