Impotence following transurethral prostatectomy is one of the main complications that still has a controversial origin. Many authors, reporting their experience, have demonstrated that this complication is due both to psychological problems and to organic causes. We review retrospectively 68 patients submitted to TURP. All patients (53 to 65 years old) were asked about their sexual efficiency before and after TURP, 6-12 months after surgery. Those who complained of erectile failure have been studied using this diagnostic protocol: plasmatic dosage of FSH, LH, Testosterone and Prolactin; penile Doppler ultrasound, polysomnographic recording of nocturnal tumescence test (NPT Test); angiography of the pudenda arteries has been performed in only one patient with pathological penile Doppler ultrasound (IPP < 0.7). The examinations demonstrated an organic impotence not secondary to vascular damage in 10 patients following surgery (incidence 15.6%). Our high incidence of this complication is, according to us, significant even if it should be considered in excess since in our study we used anamnestic criteria alone in the evaluation of sexual efficiency before surgery. In 1984 T. Lue demonstrated, through accurate histological preparations, that cavernous nerves run contiguously to the prostatic capsule at 5 and 7 hours in correspondence of the glandular apex. He suggested that impotence following TURP is due to iatrogenic lesions of these nervous structures during endoscopic resection. Similarly, we have conducted an anatomopathological study on prostate specimens taken from autopsies. We demonstrated the presence of nervous structure contiguously to the prostatic capsule in correspondence with the glandular apex. Thus, impotence following TURP probably occurs after an iatrogenic heat lesion of the periprostatic plexus caused by resection.(ABSTRACT TRUNCATED AT 250 WORDS)