OBJECTIVE Prostate-specific antigen (PSA) has become the most useful serum tumor marker in the diagnosis and screening of prostate adenocarcinoma. The currently cited reference range of normal (0 to 4.0 ng/mL monoclonal) lacks both the sensitivity and specificity to be universally accepted as a screening test, and alternatives to serum PSA have been proposed, such as PSA density, PSA velocity, and age-adjusted PSA. Age-adjusted PSA takes into account the facts that as men grow older the prostate enlarges and that screening should have maximum sensitivity in younger men and maximum specificity in older men. METHODS A population of 4,710 men with no known history of prostate adenocarcinoma underwent 5,629 examinations by transrectal ultrasound of the prostate (TRUS) from 1987 to 1994. This population consists of Mobile Urology Group, Mobile, Alabama, and Emory University, Atlanta, Georgia, patient databases. We have examined our data to determine the sensitivity, specificity, and positive predictive values for normal range PSA (0 to 4 ng/mL) versus age-specific PSA values. RESULTS A total of 2040 patients had an abnormal digital rectal examination (DRE) and 3581 procedures were performed for an elevated PSA and a normal DRE. Biopsies were performed in 2,657 patients with 945 (35.6%) positive for cancer. Criteria for biopsy included elevated PSA (more than 4 mg/mL), PSA density more than 0.15 abnormal DRE, or suspicious TRUS. Patients were grouped according to decade: group 1 (ages 40 to 49 years, n = 183), group 2 (ages 50 to 59 years, n = 1018), group 3 (ages 60 to 69 years, n = 2358), and group 4 (ages 70 to 79 years, n = 1687). CONCLUSIONS Use of the age-specific range for PSA increases the sensitivity in younger men more likely to benefit from treatment, and decreases the biopsy rate in older patients who may not be candidates for aggressive treatment. Age-adjusted PSA is the most valuable for patients over the age of 70 years of whom 22% would be spared TRUS with biopsy.