Objective To investigate cytokeratin 13(CK13) expression in nasopalatine duct cyst epithelium and its significance.Methods CK 13 expression in 36 nasopalatine duct cyst was examined by immunohistochemical technique with monoclonal antibody against CK13(DE-K13)Results CK13 showed no expression in ciliated and columnar epithelium,(-);and weak positive in the basal layers of mixed epithelia of both ciliated columnar and squamous epithelium(+); positive in basal and surface layers in some parts of squamous epithelium(++);and strongest positive in all layers of some parts of squamous epithelium (+++).Conclusion There was no expression of CK13 in ciliated and columnar epithelium,but its expression increased gradually during the metaplastic process from ciliated and columnar epithelium to squamous epithelium.CK13 may be used as a marker during the process of metaplasia from ciliated and columnar epithelium to squamous epithelium.