The authors subdivide the primary non-Hodgkin cutaneous malignant lymphomas into "proper" and "non-proper" types. "Proper" lymphomas are those which have in the skin their proper site of localization, and include mycosis fungoides, Pagetoid reticulosis, Baccaredda-Sézary syndrome and possibly lymphomatoid papulosis. They are T-cell lymphomas arising in the papillary dermis, characterized by epidermotropism, having a specific clinical feature in that they are unlikely to be simulated by other cutaneous malignant lymphomas. "Non-proper" lymphomas are those which do not usually arise in the skin, but in various other organs. They are B-, T- or null-cell lymphomas, arising in the middle dermis, infrequently epidermotropic, having a papular-nodular-tumoural clinical feature, which are indistinguishable clinically from other neoplastic types such as plasmacytoma and Hodgkin's disease. The three classifications of non-Hodgkin lymphomas most followed are not directly applicable to cutaneous lymphomas because some of the former are not primarily sited in the skin, and because a follicular morphology is infrequently seen in the latter. Whereas the first classification reported for cutaneous lymphomas utilized malignancy as a criterion, the present classification here proposed utilizes the propriety of the site of localization as the criterion for subdivision into "proper" and "non-proper" types.