We report 9 patients with an unusual plasma cell proliferative disorder of the upper aerodigestive tract. Six patients were men and three, women. The age at presentation ranged from 40 to 67 years with a mean of 54 years. Symptoms at presentation included dysphonia, dysphagia, difficulty breathing, and oral pain. These plasma cell lesions typically produced a cobblestone or warty appearance of the upper aerodigestive tract mucosa including the larynx, pharynx, palate, lips, mouth, tongue, and trachea in varying combination of multiple sites in each patient. Histologically, all lesions were characterized by psoriasiform epithelial hyperplasia with dyskeratosis and dense subepithelial plasmacytosis. Plasma cells were mature but so expansive and diffuse in infiltration as to suggest extramedullary plasmacytoma. Immunohistochemistry for kappa and lambda light chain showed polyclonal immunoglobulin content in all cases examined. Microbial cultures and Warthin-Starry stains were negative for organisms. A variety of treatments including antibiotic therapy, corticosteroid administration, and surgical resection were unsuccessful. In two patients, the process required tracheostomy. This disorder has not been previously described with the exception of a single reported case, which is included in this series. The etiology, pathogenesis, and successful management of mucous membrane plasmacytosis remain unknown.