Quantitation of serum prostate-specific antigen (PSA) has recently come into widespread use. Controversy exists regarding its usage in screening for carcinoma of the prostate (CAP), based partly on concern that it may detect small foci of CAP that will not cause any significant morbidity or mortality. This study was conducted to evaluate serum PSA levels in stage A1 CAP. The authors identified 143 consecutive men who had PSA levels drawn within 8 weeks of transurethral resection performed for presumed benign prostatic hyperplasia. One hundred twenty-four of these (86.7%) had no cancer, 11 (7.7%) were found to have stage A1 CAP, and eight (5.6%) were found to have CAP beyond stage A1. The mean PSA level in patients with stage A1 CAP was 2.3 ng/mL, and the benign (no cancer) group had a mean PSA level of 3.8 ng/mL. Ten of the 11 patients in the stage A1 group had PSA values less than 4.0 ng/mL. Therefore, it was found that most patients with stage A1 CAP did not have elevated PSA levels. In the authors' experience, elevation of PSA levels caused by CAP is indicative of a tumor burden greater than that found in stage A1 CAP.