The papilloma is the most common benign tumor of the larynx. One of the characteristic point of laryngeal papilloma is severe recurrence in spite of appropriate treatment. Therefore, many authors have made investigation into its clinical behavior and prognostic factors. This study evaluated the expression of PCNA using immunohistochemical study to search for the factors related to recurrence and clinical behavior in 18 cases of laryngeal papilloma from Jan. 1990 to May 1995. The following results were obtained : 1) Atypia was predominant and basal ratio was increased in recurrence group(p<0.05). 2) PC10 Index was higher in recurrence group(62.43%) than in non recurrence group(16.11%),(p<0.01). 3) PC10 Index was higher in multiple lesions(59.73%) than in single lesion(9.00%),(p<0.001). The positive ratio of PCNA is correlated to recurrence and type of lesion. The PCNA ratio could be useful for predicting prognosis but further investigations will be needed.