Screening for Colorectal Cancer in Older Patients (PLCO Screening Trial)

Exclusion Criteria: * Men and women who at the time of randomization are less than 55 or greater than or equal to 75 years of age * Individuals undergoing treatment for cancer at this time, excluding basal-cell and squamous-cell skin cancer * Individuals with known prior cancer of the colon, rectum, lung, prostate * This includes primary or metastatic PLCO cancers * Individuals with previous surgical removal of the entire colon, one lung, or the entire prostate (men only) * Until October 1996, women with previous surgical removal of both ovaries were excluded from the trial. In order to increase the enrollment of women into the trial, beginning in October 1996, these women were no longer excluded for this reason. * Individuals who are participating in another cancer screening or cancer primary prevention trial * Males who have taken Proscar/Propecia/finasteride in the past 6 months * NOTE: Individuals who are already enrolled in the trial when their physician prescribes finasteride are not prevented from taking this medication. As a result, these participants will continue to be screened and followed just as those participants who are not on finasteride. * NOTE: Men who are taking Tamoxifen are not excluded from any part of the PLCO Screening Trial. * Prior to April 1, 1999 women were excluded from the trial if they were currently taking or had taken Tamoxifen or Evista\\Raloxifene in the past 6 months. As of April 1999 based on a decision from the PLCO Ovary Subcommittee, women who have or are currently taking Tamoxifen or Evista\\Raloxifene are not excluded from participation. * Individuals who are unwilling or unable to sign the informed consent form * Males who have had more than one PSA blood test in the past three years * Individuals who have had a colonoscopy, sigmoidoscopy, or barium enema in the past three years