Abstract Vajner L., V. Konrádová, J. Uhlík, J. Zocová: Mucin Histochemistry of Tracheal Goblet Cells after Oral Administration of Ambroxol. Acta Vet. Brno 2001, 70: 9-13. Previous studies on the effect of various mucolytic drugs on the tracheal epithelium ultrastructure revealed ambroxol as the most harmful one. To complete these studies, we decided to evaluate the effect of ambroxol on the glycoconjugate content in the secretion of tracheal goblet cells. Using the methods of both conventional and lectin histochemistry, the percentage of tracheal goblet cells containing various glycoconjugates was evaluated. Twenty minutes after oral administration of 7.5 mg of ambroxol, goblet cells containing neutral glycoconjugates disappeared from the rabbit tracheal epithelium. Among goblet cells containing acidic glycoconjugates, the percentage of sialylated glycoconjugate-containing ones slightly decreased compared with control healthy rabbits. Oral administration of ambroxol only slightly affected the composition of glycoconjugates contained in goblet cells of the tracheal epithelium in rabbits. Tracheal goblet cells, conventional and lectin histochemistry, mucolytic drug ambroxol, rabbit Ambroxol, the most frequently used mucolytic agent in clinical practice, affects both ciliated and secretory cells in the respiratory system. It stimulates ciliary activity as well as incorporation of precursors into phospholipids in granular pneumocytes causing thus a decrement of mucus adhesion to the hypophase. According to pharmacological studies, it facilitates incorporation of hydrolytic enzymes into lysosomes of the airways' secretory cells. Activation of these acidic mucopolysaccharide-degrading enzymes leads to a decrease of the sputum viscosity (·míd and Holcát 1994). In our previous studies, reactions of the rabbit tracheal epithelium to oral administration of a single therapeutic dose of 6 various mucolytic drugs were compared. The adverse effect of ambroxol was the most pronounced (Konrádová et al. 1985ab; To complete the study, changes of the glycoconjugate content of the tracheal goblet cells were studied under the same experimental conditions using both conventional and lectin histochemistry