Studies have been performed to evaluate both the relative amounts and molecular forms of the collagens synthesized by a new cell line (HU1) established from a human lung adenocarcinoma. The collagens secreted into the culture medium and extracted from the cell layers of cultured HU1 cells were isolated after limited pepsin digestion and differential salt fractionation. More than 70% of the collagen synthesized by HU1 cells was secreted into the culture medium rather than remaining in the cell layer. Polyacrylamide gel electrophoresis under denaturing conditions of the collagens indicated the presence of components with properties corresponding to those of the chains present in the types I homotrimer, III, IV, and V collagens. Carboxymethyl-trisacryl chromatographic analysis revealed that approximately 90% of the total collagen synthesized by HU1 cells corresponded to the type I homotrimer and that the cells did not synthesize the alpha 2(I) collagen chain. Of the remaining collagen, types III, IV, and V molecules represented 6, 1, and 4%, respectively, of the total produced. These data establish the relative proportions of the collagens synthesized by cultured HU1 cells and represent one of the initial documentations of a cell line established from a carcinoma of pulmonary origin that synthesizes type I homotrimer molecules. Furthermore, these findings suggest that HU1 cells may be a useful model for investigating the molecular basis of alterations in collagen biosynthesis associated with neoplasia.