The CARET Biorepository is a valuable resource for population-based studies of the major human cancers. During CARET's twenty years of follow-up (1985-2005), we have received reports of 1,445 participants with lung cancer, 901 with prostate cancer, 433 with breast cancer, 334 with bladder cancer, 332 with colon cancer, and 1,429 with other cancers. CARET is one of the few trials that has prospectively collected serum, plasma, whole blood, blood spots (for DNA), and lung cancer tumor specimens, as well as smoking history and serial food frequency questionnaires (in some individuals for up to 12 years) in populations at high risk for lung cancer. This wealth of information in over 18,000 individuals makes the CARET Biorepository a special resource for cancer researchers. It is important that this resource be available to a wide range of researchers for hypothesis-driven studies. We have established policies for the use of the CARET Biorepository and a process for review and decision making of proposed studies. One of the important premises of these policies is recognition of the unique characteristics of the CARET population and the limited number of specimens available. It has been a policy of the CARET Steering Committee that these specimens should not be used to conduct pilot studies or methods development that can be easily conducted in other populations, but only for analyses that focus on confirming or refuting important relevant hypotheses. This website will provide investigators with background information on CARET, the findings of the trial, specimen availability, and information on how to request specimens for hypothesis-driven studies.