Between April 1994 and March 1995, transurethral balloon laser thermotherapy (TUBAL-T) using Prostalase was performed on 53 patients with benign prostatic hyperplasia. Clinical efficacy was evaluated at 3 months after TUBAL-T. The mean international prostate symptom score (I-PSS) decreased from 21.5 at baseline to 11.3 after 3 months (p < 0.0001). Irritative (the sum of items 1, 2, 4 and 7 of I-PSS) decreased by 55%, while obstructive symptoms (the sum of items 3, 5 and 6 of I-PSS) by 45%. However, other objective parameters such as maximum flow rate, voided volume, percent postvoid residual volume and prostate volume showed no significant change (7.8 to 7.2 ml/s, 130 to 147 ml, 33 to 28% and 39.7 to 41.0 ml, respectively). In conclusion, significant improvement after TUBAL-T was observed for subjective symptoms, especially irritative symptoms, but not for objective parameters.