Cholesteatoma is characterized by the presence of a squamous epithelium invading the middle ear altering its growth properties. This epithelium is belived to have hyperproliferative properties. Inflammatory stimulation of the underlying connective tissue may be reponsible for the dysregulation and abnormal proliferative feature of the keratinocytes in cholesteatoma. Comparative investigation was performed to assess the epithelial cell kinetics of cholesteatoma and auditory meatal skin. Monoclonal antibody PCNA(proliferating cell nuclear antigen) immunohistochemical staining was applied. Specimens of cholesteatoma samples (n=30) showed an average PCNA score (quotient of the PCNA positive cells and the total number of cells) of 26.6±10.1%. Auditory meatal skin (n=8) revealed an average PCNA score of 8.2±3.4%. The results of this study confirm a highly increase in the proliferation rate of cholesteatoma keratinocytes, which had an PCNA score that was 3.24 times higher than the score for keratinocyte of auditory meatal skin. Since the cholesteatoma possesses a variable degree of proliferative activities depending on its histologic composition, the formation and accumulation of the keratin due to the continuous epithelial growth probably are important element in inducing the inflammation.