Squamous cell carcinoma is the most common of human cancers, and yet because it is poorly represented by cultured cell lines, little is known about the characteristic cell biology and the cell-surface antigenic phenotypes of such tumors. To develop a continuously available source of squamous cell carcinoma for repeated and reproducible serologic analysis and for better understanding of its biologic characteristics, tissue culture methods and nude mice were used to establish new cell lines of squamous carcinoma. Special media, serum supplements from several sources, and methods of handling fresh tissue specimens were all examined as a means of improving the survival of tumor cell lines. Several new cell lines were established. Features characteristic of a squamous cell origin, eg, microvilli, desmosomes, tonofilaments, and the squamous cell differentiation antigen (pemphigus antigen), were found. The clinical course of disease in individual donor patients has been examined.