Lung cancer is the leading cause of cancer-related death in the United States. The primary risk factor for lung cancer is smoking, which accounts for more than 85% of all lung cancer-related deaths. Radon gas, a radioactive gas that is produced by the decay of radium 226, is the second leading cause of lung cancer. The decay of this isotope leads to the production of substances that emit alpha-particles, which may cause cell damage and therefore increase the potential for malignant transformation. Furthermore, data suggest that postmenopausal women who smoke or are former smokers should not undergo hormone replacement therapy, because it increases the risk for death from non-small cell lung cancer. Important changes in these NCCN Guidelines for 2010 include updates to the Principles of Surgical Therapy and Radiation Therapy, and the addition of a section on maintenance therapy for advanced or metastatic disease. In addition, recommendations for a number of chemotherapy regimens were modified, including the addition of erlotinib as a first-line treatment option for patients who are positive for the EGFR mutation, and staging was updated per the IASLC recommendations. © Journal of the National Comprehensive Cancer Network.