Heat shock proteins (hsps) are essential for the survival of cells under an environmental insult. To elucidate the relationship between these intracellular proteins and acute otitis media (AOM), the authors studied hsp production in guinea pigs with AOM induced by inoculation of Streptococcus pneumoniae into the middle ear. Animals were sacrificed 1, 3, or 5 days after inoculation. Immunocytochemical study showed localization of hsp70 within the epithelium of infected ears, while the normal control epithelium showed very light staining. Western blot tests of the mucosal extraction confirmed the presence of hsp70 in otitis media. Enzyme-linked immunosorbent assay (ELISA) showed that hsp levels were higher in the infected mucosa than in the normal control mucosa. In contrast, hsp60 was not stimulated in infected ears. This study showed that hsp70, and not hsp60, was produced in the AOM model.