The Etiologic and Early Marker Studies (EEMS) is a component of the Prostate Lung Colorectal and Ovarian (PLCO) Trial. By collecting biologic materials and risk factor information from participants, PLCO EEMS provides a rich resource for research on cancer etiology and early detection biomarkers. The PLCO Biorepository stores approximately 2.9 million biologic specimens collected from PLCO participants. These specimens and their associated data are available to all qualified researchers through an application and peer-review process. EEMS also covers tissue specimens from the LSS component of the National Lung Screening Trial (NLST).