BACKGROUND While prostate specific antigen (PSA) is useful as a tumor marker for monitoring patients with prostate cancer after definitive therapy, limitations have been noted when it is used for early detection of prostate cancer. METHODS We reviewed the charts of 121 patients who had undergone prostate needle biopsies, documented digital rectal examination (DRE) and serum PSA determination before biopsy from January 1993 to October 1994. Indications for biopsy included abnormal DRE. PSA level greater than 4.0 ng/ml or abnormal lesions on transrectal ultrasonography (TRUS). RESULTS Seventeen patients (14%) had stage A carcinoma with normal DRE and PSA levels from 0.1 to 34.9 ng/ml (mean 9.0 ng/ml). Four patients (3%) had stage B carcinoma with an average PSA level of 32.3 ng/ml and less than one lobe indurated on DRE. Six patients (5%) had stage C carcinoma and had an average PSA level of 48.5 ng/ml and less than one lobe indurated on DRE. Ninety-four (78%) patients had stage D carcinoma with an average PSA level of 120 ng/ml and more than one lobe indurated on DRE. While hypoechoic sectors were more than twice as likely as isoechoic sectors of the prostate to contain malignancy on biopsy, nearly 20% of cancers were found in isoechoic sectors. CONCLUSIONS Serum PSA is the most accurate of the three diagnostic tests evaluated. The addition of DRE or TRUS improves the detection rate of prostate cancer over PSA alone.