We present six patients in whom Langerhans' cell granulomatosis (histiocytosis X) was found in lymph nodes also harboring malignant lymphomas: Hodgkin's disease in five and non-Hodgkin's lymphoma in one. This brings to 12 the total number of such reported cases. Whether this represents a chance association of the two processes or a peculiar reaction of Langerhans' cells to the lymphoma is unknown. The focal intimate intermingling of the two processes and the inability to identify LCG as an incidential finding in other cancers suggests that this phenomenon may represent a peculiar reaction to the lymphoma.