Review of the literature and the study of a case associated with a malignant lymphoma strongly suggests that the Sézary syndrome is merely a clinical variant of mycosis fungoides. Additional evidence is presented that the lymphadenopathy of the Sézary syndrome is not always of a benign nature, as originally indicated in the literature. Both the Sézary syndrome and mycosis fungoides share the unpredictability of the neoplastic processes of the reticular system which are likely to involve simultaneously or successively, the skin and the lymph-hematopoietic system, as well as the ability of the cell involved in the process to invade the blood stream, giving rise to the leukemic variety of the malignant reticulosis.