In a histological study of biopsy and postmortem material from 30 cases of nasal disease in which a clinical diagnosis of 'midline granuloma' or Wegener's granuloma had been given, we selected 10 cases on the basis of the presence of widespread coagulative necrosis and atypical cells. Evidence is provided that such changes represent a malignant neoplasm of histiocytic lymphoma type. Local invasion and spread to cervical and more distant lymph nodes, spleen, liver, and kidney were seen in some of the cases. Erythrophagocytic activity was marked in the spleen in three cases and histiocytic infiltration of the bone marrow in two cases, indicating a more generalised activity of histiocytic cells. Terms such as 'malignant granuloma' should be abandoned. In obstructive and ulcerating conditions of the nose efforts should be concentrated on making an accurate histological diagnosis.