Glycoprotein MUC8, one of the less studied mucins, belongs to the group of soluble mucins. Its cDNA is only partially cloned. Like other mucins, MUC8 has a tandem repeat containing domain, but in contrast to other mucins, which have, as a rule, only one type of repeats, the MUC8 mucin has two types of repeats: one of 13 amino acids and another one containing 41 amino acid residues. The MUC8 gene is localized on human chromosome 12q24.3. MUC8 mucin appears to serve a ciliated cell marker. Regulation of MUC8 gene expression has been studied and some regulatory pathways have been identified. MUC8 mucin plays a major role in the airway mucosa and its over-expression and hypersecretion are associated with airway inflammatory diseases.