We describe a novel human bronchial epithelial cell line immortalized after transfection with the E6 and E7 genes of human papillomavirus type 16. The established HBE4-E6/E7 cell line resembles morphologically the basal cells of the normal human bronchial epithelium and is nontumorigenic. A clonal isolate proved to be more sensitive to terminal differentiation induced by phorbol esters than the parental line, but both are refractory to the effects of serum. HBE4-E6/E7 cells are able to form tubules when grown in a basement membrane-like matrix, indicating that the cellular pathways leading to immortalization and those governing morphogenesis are distinct. This cell line should prove useful in the study of bronchial epithelial cell growth, differentiation, morphogenesis, and carcinogenesis.