We are only beginning to understand the importance of lung cancer tumor biology in relation to prognosis and response to therapy. Many of the biologic and genetic changes we have described are preliminary observations and require further confirmation before clinical use. However, information concerning three oncogenes may soon prove to be helpful in the clinical arena: the myc genes in SCLC, and the ras genes and c-erbB-2 in NSCLC. In general their presence identifies poor patient response to therapy and poor survival. These markers are currently being used in a clinical setting at some research centers, but are not recommended for general diagnostic or prognostic use without further confirmation of their utility. Incorporation of this information with that learned by standard staging procedures may result in improved understanding of patient prognosis and challenge current concepts of lung cancer treatment. For example, surgically resected stage I NSCLC patients may benefit from adjuvant therapy if found to have these adverse biologic factors, and require more stringent follow-up after therapy. Finally the understanding of the pathogenesis of lung cancer may enable the development of novel therapy directed against these growth pathways. Our ultimate goal is to derive a therapeutic and prognostic paradigm involving both molecular-genetic and clinical factors to arrive at an optimal staging model and treatment plan.