This study was undertaken to determine quantitative histologic changes after a single episode of acute suppurative otitis media in the rat middle ear mucosa, with special reference to goblet cell density, and to determine the persistency of these changes. Drum vascularization, purulent effusion, mucosal thickness, bone and subepithelial gland formation was assessed. Twenty-five rats were inoculated with viable pneumococci type 3 through the right, bony middle ear bulla. The left bulla served as control. At days 4, 8, 16, 90, and 180 after inoculation, five rats were sacrificed on each occasion; the bullae were removed, opened, and divided into two halves, which were stained according to the periodic acid-Schiff (PAS)-alcian blue method. The stained mucosa was dissected from the bone and placed in an anise oil-colophonium chamber, for determination of interindividual median density and range of goblet cells by light microscopy. Counting was performed in 24 well-defined localities, covering the entire bulla mucosa and the drum. Areas normally containing goblet cells were extended. Goblet cell density was significantly (Mann-Whitney, p < .05) increased in almost all localities, reaching a maximum at day 16, whereafter the mucosa normalized. All changes quantitated, except drum vascularization and purulent effusion, were persisting at day 180. Cobblestone appearance of the epithelial surface and polypous mucosal prominences were found. Mucosal thickening was prominent in areas covered with flat epithelium, less so in other areas. Local differences in the degree of increased mucosal thickness were preventing intrinsic tubal occlusion. Enhanced secretory ability of the middle ear mucosa was persisting 6 months after a single episode of acute suppurative otitis media, perhaps predisposing secretory otitis media.