Lung cancer is the most common cause of cancer death in the United States among both men and women, with an estimated 177,000 new cases and 159,000 deaths in 1996. Its overall incidence is increasing, particularly in women, and despite many complex and aggressive approaches to therapy, and great strides in understanding its biology and etiology, corresponding improvements in outcome are not yet apparent. This article will summarize the state of knowledge of the biology and genetics of lung cancer. These and future advances in our knowledge will certainly provide the foundation for future advances in therapeutics.