Human papillomaviruses (HPV) are associated with papillomatosis of the larynx, trachea, and bronchi in decreasing order of frequency, and these papillomatosis lesions may become malignant. When the patients are not selected for a history of papillomatosis, the frequency of HPV in bronchogenic carcinoma tissue is 1-5%. In order to develop a model for investigating the role of HPV in human bronchogenic carcinogenesis, normal human bronchial epithelial cells were transfected with cloned full-length HPV16 or HPV18. Two HPV18-transformed cell lines (BEP1 and BEP2) and one HPV16-transformed cell line (BEP3) were established. These nontumorigenic epithelial cell lines have: (a) attained over 100 population doublings in vitro; (b) mutually exclusive human marker chromosomes; (c) HPV DNA in forms that are consistent with chromosomal integration by Southern analysis; (d) HPV E6, E7, and E6* mRNA transcripts by Northern and reverse transcriptase-polymerase chain reaction analysis; and (e) diminished confluence-induced squamous differentiation. These cell lines should be useful for studying mechanisms involved in proliferation, differentiation, and neoplastic transformation of human bronchial epithelial cells.