The status of middle ear effusion and histopathological changes in the subepithelial space of the mucosa from a well documented temporal bone with blue eardrum in one ear and chronic otitis media with effusion (OME) in the opposite ear were investigated using morphometry at four different locations within the middle ear cleft. Our findings indicated that histopathologies of the blue eardrum were similar to those of OME except for the appearance of increased hemosiderin-laden macrophages in the subepithelial space and effusion, which seemed to be an evidence of hemorrhages. The recurrent hemorrhage, still unexplained, constituted the primary factor in the pathogenesis of the blud eardrum, whereas subepithelial changes and cholesterol granuloma also seen in OME were considered to be the secondary pathologies of hemorrhage in the middle ear cleft, which occurred in the course of OME. We suggest that the idiopathic blue eardrum has a possibility of the condition which recurrent hemorrhages occur in OME, rather than a different phase of OME.