The incidence of impotence following transurethral resection of the prostate (TURP) for benign prostatic hyperplasia (BPH) was investigated, as well as its correlation with the localization of peroperative capsular perforations and the amount of prostate tissue resected. Patients underwent an interview questioning their potency before and after TURP. For each patient, the TURP technique was reviewed: the localization of eventual capsular perforations was noted and the amount of tissue resected was recorded. Of the 100 patients assessed, 83 were anamnestically potent prior to TURP. Of these, 27 (##%) reported complete loss of erections after operation. Peroperative capsular perforations adjacent to the neurovascular bundles and small-size adenomas correlated significantly with postoperative impotence. The results suggest that capsular perforations adjacent to the neurovascular bundles may be a cause of impotence after TURP, and that patients with small-size adenomas bear a higher risk of post-TURP erectile dysfunction.