While the overall survival of patients with lung cancer has remained relatively unchanged over the past decade, there have been major advances in our understanding of the biology of small cell and non-small cell lung cancer through the study of lung cancer cell lines. Surface molecules associated with lung cancer have been identified and their molecular structure and function are being elucidated. Growth factors which stimulate the lung cancer cells in an autocrine fashion have been identified. Genetic changes of lung cancer cells have been defined on a chromosomal and a molecular level. This review summarizes many biologic properties of lung cancer cells that have been described in the literature.