A longitudinal sequential study of otitis media was done in an experimental animal (cat) using eustachian tube obstruction. Fifty animals were used. Cellular infiltration of the tensor tympani and stapedius muscles was studied in a continuum from day 1 to 6 months after inducing otitis media. We observed that there is infiltration of the connective tissue of both muscles in otitis media, and that the cellular changes follow the same pattern as that seen in the mucoperiostium and the round window of the middle ear, although to a lesser degree. In this first report of sequential changes in middle ear muscles in otitis media, clinical implications of these findings are discussed.