Transrectal ultrasound of the prostate (TRUS) plays a major role in the follow-up of hormonally treated D2 prostate cancer patients because in these situations the digital rectal examination (DRE) cannot be reliable in the evaluation of local recurrence. 82 patients with advanced prostate cancer were evaluated. Mean follow-up was 33 months (range 3-103). TRUS was performed before starting hormonal therapy and every 3 months thereafter. A volume decrease of the prostate was obtained in 91% of the patients. The lowest mean volume of the prostate (nearly 55% decrease of the pretreatment volume) was reached after 6-9 months of therapy. 62.1% of the patients underwent disease progression after a mean follow-up of 25 months (range 3-80). No correlation between systemic progression and ultrasound findings were observed. In 9.6% of cases a local progression was observed. In 42 patients PSA was used in association with TRUS: the PSA nadir was reached after 6-9 months of therapy. PSA increased in every case a disease progression was observed. The data showed that TRUS is an objective and reliable method in the follow-up of D2 prostate cancer patients. However, considering the low incidence of local progression, the use of PSA appears to be the standard method to monitor the patients, leaving TRUS in case of suspicion of local progression.