Background: The benefit of screening for prostate cancer using prostate-specific antigen (PSA) testing and digital rectal examination (DRE) is uncertain and is under evaluation in a randomized prospective trial, the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial. Although the final results are several years away, the initial round of screening is complete. We describe the population enrolled in the PLCO trial, their baseline PSA and DRE screening results, and diagnostic follow-up results during the first year of follow-up. Methods: A total of 38 350 men were randomly assigned to the screening arm of the PLCO trial from November 1993 through June 2001. Men were advised to seek diagnostic follow-up from their primary care provider if their DRE was suspicious for cancer and/or if their serum PSA level was higher than 4 ng/mL. PLCO trial staff obtained records related to diagnostic follow-up. Results: Compliance with both screening tests was high (more than 89%). At screening, 7.5% of men had a positive DRE (i.e., suspicious for cancer) and 7.9% had a PSA level higher than 4 ng/mL. Of the men with positive screening tests, 74.2% underwent additional diagnostic testing, and 31.5% underwent a prostatic biopsy within 1 year. Overall, 1.4% of the men in the screening arm were diagnosed with prostate cancer, the majority of whom had clinically localized cancer. These compliance, biopsy, and cancer detection rates appear to be representative of contemporary practice patterns. Conclusion: The PLCO trial is evaluating PSA- and DRE-based screening for prostate cancer in a clinically valid manner. Whether such screening will result in a reduction of prostate cancer mortality cannot be answered until the randomized comparison is completed.