Immunologic function of the epithelium, especially epidermal Langerhans' cells(LC), may enable us to determine the role of epithelium in cholesteatoma formation. The epidermal LC are thought to be sentinel cells of the cutaneous immune surveillance system. They are dendritic cells of bone marrow derivation which reside mainly within stratified squamous epithelium. LC have HLA-DR antigen(Ia antigen), Fc-IgG, C3b receptor and OKT-6 antigen on the cell surface. Custodial function of LC is always carried out in close relation with T lymphocyte. On the basis of evidence that lymphocytes present in cholesteatoma matrix are identified mostly as T lymphocytes, it is believed that cell mediated immunity is involved in cholesteatoma. This report described and compared the LC, T lymphocytes, T cell subset and B lymphocytes in posterior auricular skin and cholesteatoma matrix. Both of transmission electron microscope and immunohistochemical staining were employed to demonstrate the localization of LC, T lymphocytes, T cell subset and B lymphocytes.