PSA has become the most important tumor marker in prostate cancer and has increased its usefulness from simply being a marker of treatment response, to one of early detectible/screening, and more recently as an aid in staging. Lymph node status in patients with prostate cancer is extremely important in terms of prognosis and treatment. We therefore undertook this study to evaluate the predictive value of PSA in determining lymph node status in an attempt to limit the number of lymph node dissections. The study consists of 240 consecutive cases of prostate cancers having pre op PSA levels, negative bone scans and known lymph node status (determined by lymphadenectomy). Results showed that the risk of node positive disease highly correlated with PSA levels and poorly correlated with clinical stage and histologic grade. There was no minimal PSA level under which nodes were consistently negative. With PSA under 10, 7.7% of lymphadenectomies revealed at least one positive node (2 cases had PSA's of 3). When PSA was between 10 and 20, 17% had positive nodes, with PSA between 20 and 50, 21% were node positive, and 53% positivity when PSA was over 50. The combination of low grade tumors with PSA under 20 identified a subgroup of patients with consistently negative nodes. We therefore conclude that PSA levels may be of use in predicting lymph node status but cannot, at present, be used to replace lymphadenectomy.