To determine if the preoperative variables of serum prostate specific antigen (PSA), primary Gleason grade from the biopsy specimen and local clinical stage as determined from digital rectal examination can accurately predict the pelvic lymph node status in patients with clinically localized prostate cancer, we reviewed the medical records of 1,632 patients who underwent bilateral pelvic lymphadenectomy at our institution between January 1988 and December 1991. Using logistic regression analysis, serum PSA was found to be the best predictor of pelvic lymph node metastases (p < 0.0001). The predictive power of serum PSA could be enhanced considerably by taking into account the Gleason grade (p < 0.001) and local clinical stage (p < 0.001). A statistical model using all 3 variables was developed that allows the practicing urologist to estimate on an individual basis the probability of pelvic lymph node involvement. Using a conservative cutoff point of less than 3% as an acceptable false-negative rate, 61% of the patients with clinical stages T1a to T2b (A1 to B1) disease and 29% of those with clinical stages T1a to T2c (A1 to B2) prostate cancer may be spared an open or laparoscopic staging bilateral pelvic lymphadenectomy. As a result, patient morbidity can be decreased and a significant economic savings to the health care system can be realized. This observation has particular importance for prostate cancer patients being managed with radical perineal prostatectomy or definitive radiation therapy.