1. The acidic and neutral glycoproteins secreted by cultured tracheal explants from pigs, sheep, rats, mice, monkeys, guinea pigs, dogs and chickens were purified and fractionated by column chromatography on DEAE-cellulose and by electrophoresis on cellulose acetate. 2. The ratios of acidic to neutral mucus glycoproteins were compared for the above animals with that of mucus glycoproteins secreted by cultured human bronchi. 3. The observed ratios of acidic to neutral glycoproteins ranged from 4.0 (mouse) to 7.2 (chicken and pig) from cultured tracheae; secreted human bronchial mucus had a ratio of 2.7. 4. The ratio of acidic to neutral glycoproteins secreted by tracheal explants varied with duration of incubation of the trachea in culture.