The purpose of this report is to update a previous evidence review commissioned by the U.S. Preventive Services Task Force (USPSTF) on screening for lung cancer. In 2004, based on the previous evidence review, the USPSTF found there was insufficient evidence to either recommend for or against routinely screening asymptomatic persons for lung cancer with either low-dose computed tomography (LDCT), chest x-ray (CXR), sputum cytology, or a combination of these tests (I statement). Lung cancer is a proliferation of malignant cells arising in the airways or tissues of the lung. Ninety-five percent of lung malignancies are either non-small cell lung cancer (NSCLC) or small cell carcinoma, with small cell carcinoma accounting for 16 percent of cases. The remaining 5 percent of primary pulmonary malignancies include rare entities such as carcinoid tumor. NSCLC is a heterogeneous designation with subsets including squamous cell carcinoma, adenocarcinoma, large cell carcinoma, and undifferentiated carcinoma. Individual tumors can show features of several of these subtypes. Adenocarcinoma is the most common subtype, encompassing 36 percent of all lung cancers, with squamous cell carcinoma making up 20 percent of cases in a large survey of U.S. lung cancer from 1998 to 2001. The World Health Organization has recently revised the histology classifications for lung cancer, including several new preinvasive lesions within the adenocarcinoma classification. Lung cancer is the second most commonly occurring cancer in the United States among men and women and the leading cause of cancer-related death. The American Cancer Society (ACS) predicted there would be approximately 226,160 new cases and 160,340 lung cancer