We studied 48 cases of amyloidosis localized to the lower respiratory tract. Fourteen cases were classified as tracheobronchial amyloidosis. Twenty-eight cases showed solitary or multiple nodules, and six cases had a diffuse interstitial parenchymal pattern. Almost all patients with tracheobronchial and diffuse interstitial amyloidosis had respiratory symptoms (usually dyspnea), whereas most with nodular amyloidosis were asymptomatic. Nodular parenchymal and, less frequently, tracheobronchial amyloidosis had contiguous cellular infiltrates of plasma cells, lymphocytes, and giant cells. Immunohistochemical staining of specimens from 18 cases showed these plasma cells to be polytypic, except for two tracheobronchial lesions that had a disproportionate number of lambda light chain-bearing plasma cells. Permanganate oxidation of specimens from 19 cases showed patterns in keeping with immunoglobulin-derived amyloid in 12. Local deposits of amyloid in lung may arise from deposition of circulating precursor proteins.