Clinical and pathologic data on 40 patients (31 men, 9 women) with polymorphic reticulosis are presented. The disease may involve the upper respiratory tract, notably the nose, paranasal sinuses, nasopharynx, or palate, as well as the lung, skin, gastrointestinal tract, and central nervous system. Polymorphic reticulosis is identical pathologically to lymphomatoid granulomatosis. Localized disease, particularly that in the upper airway, responds well to radiation therapy. Corticosteroids and cytotoxic agents appear to be ineffective with multisite involvement.