To evaluate the diagnostic efficacy of transrectal ultrasound (TRUS)-guided biopsy of the prostatic fossa in men with biochemical relapse following radical retropubic prostatectomy (RP). Thirty patients, with detectable prostate specific antigen (PSA) and negative imaging for metastases after RP, were evaluated for local recurrence. All patients underwent TRUS-guided biopsies of the prostatic fossa, with at least six cores obtained. PSA and digital rectal examination (DRE) were correlated with biopsy results. Twelve patients (40%) were found with local recurrence. Sensitivities of TRUS and DRE were 75 and 50%, while specificities were 83 and 100%, respectively. Local recurrence was detected in 25% of the patients with PSA <or= 1 ng/ml, and higher PSA levels were correlated with an increased positive biopsy rate. All patients with positive DRE had positive biopsy and positive TRUS as well. When both TRUS and DRE were positive it was more likely for the patient to have positive biopsy than when both TRUS and DRE were negative. TRUS-guided biopsy is an efficient tool in detecting local recurrence after RP and should be offered to all patients with biochemical relapse and absence of metastatic disease irrespective of the level of PSA.