The clinical records and histologic materials from 7 cases with malignant lymphoma (ML) in the nose were examined, and the results were compared to those in malignant histiocytosis (MH) presenting as lethal midline granuloma previously reported by us. The main differences in the clinical findings were 1) younger initiation of the disease in MH than in ML (mean values were 56 and 37 years of age, respectively); 2) ML showed a polypoid nasal mass with necrosis but MH showed necrotic granulomatous lesions; and 3) much better survival in ML than in MH. The histological findings of malignant lymphoma differed from malignant histiocytosis not only in monotony but also in cytologic details. Alpha-naphthyl acetate and butyrate esterase reactions gave clear distinction between the two diseases. From these findings, we conclude that malignant lymphoma should be clinicopathologically separated from malignant histiocytosis.