With the object to disclose an association between laryngeal papillomatosis and laryngeal carcinoma, we reviewed 102 patients with laryngeal papillomatosis treated between 1950 and 1979. Seven cases of laryngeal carcinomas were recorded and 1 patient with spread of papilloma to the bronchial tree developed a bronchial carcinoma. The time between onset of papilloma and diagnosis of carcinoma was 4-55 years (mean 24 years). For laryngeal carcinoma the ratio of observed to expected cases was 88. Of the 8 patients developing respiratory tract carcinoma, 2 had received treatment with radiation and 2 had been treated with Bleomycin. Four of these 8 patients were known smokers. This study shows that papillomatosis is more often associated with laryngeal carcinoma than previously reported. It appears, however, that laryngeal papillomas alone seldom induce carcinomas. Apart from irradiation and smoking, Bleomycin could be an important co-factor.