Juvenile laryngotracheal papillomatosis (JLTP)--a disease characterized by the growth of multiple, recurrent, koilocytolic papillomas of the upper respiratory tree--occurs in 1,500 to 2,000 infants and children in the United States every year. In rare instances, the papillomas, which are thought to be caused by a human papillomavirus (HPV), may extend into the distal bronchi and lungs. They are often excised surgically or by laser resection, but may regress spontaneously. Patients who receive radiation or cytotoxic drugs for this condition, or subsequently become smokers, may be predisposed to the development of bronchopulmonary carcinoma. Only six cases of bronchopulmonary carcinoma arising in persons with a history of JLTP but no history of these predisposing factors have been reported. Herein, we report the occurrence of squamous carcinoma of the left lung in a 28-year-old woman with JLTP since the age of 2 1/2 years. The carcinoma as well as randomly chosen papillomas excised over a period of years demonstrated positive nuclear staining for papillomavirus structural antigen. This is consistent with the current belief that human papillomavirus may be an important factor in the development of squamous carcinomas in various anatomic locations.