Objectives. To assess the prognosis of patients with bladder neck (BN) involvement in radical prostatectomy specimens and compare it with patients with seminal vesicle invasion (SVI) presumed to have an inferior stage according to the TNM classification. Methods. Two hundred eighty-six case files of consecutive radical prostatectomies were reviewed. The records of patients with pathologic BN involvement (pT4a) or SVI (pT3c) were thoroughly analyzed and compared. The mean and median follow-up periods were 30.8 and 35.5 months (range 9 to 40), respectively, for the patients with Stage pT4a and 40.8 and 44.1 months (range 8 to 86), respectively, for the patients with Stage pT3c. Particular attention was paid to the preoperative clinical and pathologic evaluation, the pathologic analysis of the prostatectomy specimen, and the postoperative follow-up data. Progression was defined as a prostate- specific antigen level of 0.2 ng/mL and rising. Adjuvant therapy was not initiated unless prostate-specific antigen failure had occurred. Results. BN involvement was identified in 25 patients (8.7%) and SVI was found in 26 patients (9.1%). In 7 patients (2.4%), the BN was the only site of positive margins. Thirty-six percent of patients with BN involvement and 62% of patients with SVI demonstrated biochemical progression. Disease-free survival and metastasis-free survival rates were significantly better for the patients with Stage pT4a than for the patients with Stage pT3c at 24 and 36 months after surgery. Univariate analysis identified the prostate-specific antigen nadir to be the most significant predictor of prognosis. Conclusions. In this study, BN involvement in the surgical specimen carried a lower risk of progression than SVI. On the basis of our preliminary results and those in other studies, a conceivable downstaging of BN involvement in the TNM staging system should be considered. Possibly, additional modification of the TNM staging system should be contemplated on the basis of the results of pathologic analysis and prognosis. The significance of BN involvement and the role of adjuvant therapy in this group of patients need further evaluation. (C) 2000 Elsevier Science Inc.