Primary Human Tracheal Epithelial Cells (HTEpC) are isolated from the surface epithelium of human trachea and stain positive for cytokeratin. The respiratory epithelia are responsible for the lubrication of the lungs, the maintenance of humidity, and the cleaning of the respiratory tract. They are an important target for drugs, toxins, and carcinogens. In addition, they are involved in many diseases such as cystic fibrosis. Consequently, HTEpC are useful for investigating the function and pathology of the respiratory system.