The histology of the bronchial specimens derived from 104 patients with an established invasive bronchial squamous cell carcinoma was assessed with special reference to the detection of the morphological manifestations of human papilloma virus (HPV) recently described in the uterine cervix, i.e., three different types of condylomatous lesions (papillomatous, flat and endophytic). Histological lesions fulfilling the criteria of papillomatous condyloma were found in 6 cases, those of endophytic condyloma in 4 cases, and lesions identical to flat type condyloma of the uterine cervix were encountered in 26 cases (25%). The role of HPV in the development of these lesions and their relationship to squamous cell carcinogenesis was discussed, and a concept hypothesizing the development of bronchial squamous cell carcinoma is outlined.