Histochemical localization of sialomucins and sulfated polysaccharides have been demonstrated in the mucous membrane of the middle ear in different middle ear effusions. Inasmuch as a more neutral stain with alcian blue-PAS is still present after treatment with neuraminidase, it is strongly suggested that neutral polysaccharides coexist with neuraminic acid in the middle ear glycoproteins. Sulfated polysaccharides are present only in the mucoid effusions. The use of precise nomenclature for mucosubstances is strongly recommended and is outlined. The nature of the specificity of the histochemical stains is discussed.