A retrospective study was performed to evaluate the clinical and pathologic characteristics of 60 patients with a palpably benign prostate gland, but with biopsy-proved prostate cancer. All patients underwent prostate biopsy because of elevated serum prostate-specific antigen (PSA) concentration, and subsequently underwent radical retropubic prostatectomy (RRP). Similar analysis was performed for a randomly selected group of 60 clinical Stage B1 prostate cancers from the same period (control cohort). Patients with nonpalpable prostate cancers had a higher preoperative PSA level as compared with the clinical Stage B1 group (median value: 12.3 ng/mL versus 4.6 ng/mL, p < 0.001). There was no significant difference between the two groups with regard to clinical parameters (voiding symptoms, hematuria, age). The nonpalpable prostate cancers exhibited a significant tumor volume (mean: 7.4 cc; range: 0.3-56 cc), and 18 (30%) demonstrated capsular perforation to involve the periprostatic tissues. Of these, three (5%) had seminal vesicle invasion, and one (2%) had pelvic lymph node involvement. There was no difference between these pathologic characteristics and those of the clinical Stage B1 prostate cancers. These findings suggest that nonpalpable prostate cancers identified by an elevated serum PSA level can be of clinical significance and warrant therapeutic consideration. Although nonpalpable, these cancers are peripherally located and were clinically suspected prior to biopsy. Therefore, we propose that these cancers be classified as clinical Stage B0 in the Whitmore-Jewett staging system; in the new TNM staging system, they are designated as clinical Stage T1c.