A case of localized lymphoplasmacytoid lymphoma of the skin was studied by light and electron microscopy, by immunological methods, and by enzyme cytochemistry. It illustrated usual and unusual features of a type of B-cell lymphoma in the skin and presented problems in differential diagnosis. Histologically, its cellularity varied from a monomorphous to a pleomorphic pattern that was highly suggestive of a nonspecific inflammatory reaction or a pseudolymphoma, but from the presence of a clone of IgG (lambda)-producing plasmacytoid cells, it was established that it consisted in fact of lymphoplasmacytoid and polymorphic subtypes of an immunocytomatous lymphoma.