Multiple parameters were examined preoperatively to determine if any could predict successful voiding after prostatectomy in male patients who present in acute urinary retention due to benign prostatic hypertrophy. A total of 50 men 50 to 85 years old (mean age 69.5 years) who presented with this clinical picture was investigated with multichannel urodynamic studies, and completed the American Urological Association (AUA) symptom score for benign prostatic hypertrophy preoperatively and postoperatively. All patients underwent prostatectomy. Mean retention volume was 1,172 cc (range 500 to 2,100). Mean preoperative and postoperative AUA symptom scores were 15.5 and 5.0, respectively. At 3 months postoperatively 45 patients (90%) were able to void without catheterization. At 16.6 months 5 patients still required clean intermittent catheterization to empty the bladder. Postoperatively, there was a statistically significant improvement in AUA symptom score, opening voiding pressure and peak flow rate. The AUA symptom score was not predictive of either impending acute retention or normal voiding after prostatectomy. In our patients no preoperative parameters were statistically different between those voiding and those on clean intermittent catheterization. However, poor sensation, large retention volumes, lack of instability and no voluntary detrusor contractions were more common in the nonvoiding men.