AbstractThe optimal tumor marker for prostate cancer would be effective for early detection, staging, and monitoring patients after definitive treatment. This marker would have a high sensitivity, specificity, and positive predictive value for distinguishing men with benign prostatic hy‐perplasia (BPH) from men with early prostate cancer. Such a marker would consistently detect biologically significant disease, correlate with clinical and pathologic staging, and predict prognosis. In addition, this marker would be accurate at indicating cure or progression of disease after treatment. Certainly, the ideal marker also would be reproducible, inexpensive, generate results rapidly, be easy to perform, be accessible to clinicians, and tolerable to patients. Unfortunately, such a “super” marker does not exist at this time. However, prostate‐specific antigen (PSA) has many of the aforementioned capabilities. This article will describe the current utility of PSA in the diagnosis and staging of prostate cancer. © 1995 Wiley