A total of 500 patients with extracapsular extension (clinical Stage C) carcinoma of the prostate received definitive radiotherapy directed to the prostate and the regional lymphatics. Pretreatment evaluation of the regional lymphatics was optional and was done in 245 patients who underwent either staging laparotomy or lymphangiography. The remaining 255 patients had no nodal evaluation. In 72 of the node-evaluated patients there was evidence of spread to the pelvic lymphatics and in 173 patients lymph nodes were negative. The three populations (lymph nodes-not evaluated, lymph nodes-involved, and lymph nodes-not involved) were analyzed as to the distribution of the recognized prognostic variables and compared as to the study end points (locoregional failure, incidence of distant metastases, disease-free survival, and survival).