Paraffin sections from 36 laryngeal squamous cell carcinomas with histological features of coexistent condylomatous changes (the flat, inverted and papillomatous lesions caused by human papilloma virus; HPV) were stained for HPV antigens with an indirect immunoperoxidase technique. The HPV antiserum used was prepared in guinea pigs immunized against the purified HPV virions from human common wart tissue. Of the tumors studied, 36% showed the presence of HPV antigens. In that, one-third of the flat and inverted lesions and 42% of the papillomatous lesions contained cells with intranuclear HPV-staining reaction. The role of HPV as the etiologic agent of laryngeal squamous cell papillomas is discussed, as is the potential malignant transformation of them. Based on the present results, the previously expressed view on the probable role of HPV in the development of laryngeal squamous cell carcinoma seems to gain further substantiation.