285 affected by BPH have been evaluated by transrectal ultrasound. All the patients had a palpably normal prostate without abnormality suggestive of cancer. 56 patients (19.6%) presented ultrasonic abnormality areas. Under ultrasound guidance, biopsy was done by the transperineal route and biopsy material showed the presence of prostatic carcinoma in 24 patients (8.3%). 6 of these had neoplasm in the non peripheral zone. The study suggests the validity of ultrasound, in particularly transrectal ultrasound, in the identification of non palpable prostatic cancer. In conclusion ultrasound appears very useful in the preoperative evaluation of the patients affected by BPH in order to identify neoplasms non detectable with other methods.