Postoperative bladder outflow was assessed in 150 patients subjected to radical retropubic prostatectomy for clinically localized prostate cancer. The overall mean (+/- S.E.M.) postoperative peak flow rates and residual urine volumes were 16.9 +/- 1.3 ml/s and 11.4 +/- 2.1 ml. According to flow nomograms, 22% of the patients were still obstructed postoperatively due to stricture of either the anastomosis or the urethra (12%), or to partial bladder denervation (10%). Scoring of subjective symptoms was not reliable in detecting postoperative outflow obstruction, while uroflowmetry with flow nomograms identified all obstructed cases. Radical retropubic prostatectomy can induce both mechanical and functional alterations of the distal urinary tract and a strict assessment of postoperative bladder outflow is recommended.