PURPOSE: To evaluate the usefulness of US-guided transrectal biopsy with automated biopsy gun in prostatic disease. MATERIALS AND METHODS: We retrospectively reviewed the result of TRUS-guided prostatic biopsy. TRUS was performed in 107 patients who were clinically suspected of prostatic disease, 44 patients underwent TRUS-guided transrectal prostate biopsy by automated biopsy gun mounted with 18-gauge, 20 cm biopsy needle. The patients were examined in transverse and longitudinal planes by TRUS with 7-MHz transducer. The criteria for biopsy were a hypoechoic nodule located in prostatic parenchyma, asymmetrical enlargement, coarse echogenicity, and elevated serum PSA level. Biopsy was performed two or three times at the hypoechoic nodule with systematic biopsy at normal appearing prostate and three or four foci at the peripheral and central portion randomly if the focal lesion was not seen. RESULTS: Forty four biopsies were done. Sufficient tissue for the histopathologic diagnosis was obtained in 41 patients (93.2%). Histopathologically, there were cancer in 10 cases and benign diseases in 31, Ten patients with hypoechoic nodule were cancer in four cases, nodular hyperplasia in five and infiammation in one. On random biopsy in 31 cases there were cancer in six cases, nodular hyperplasia in 21 and inflammation in four. The sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of TRUS for cancer were 40%, 81%, 40%, 81% and 71%. There was no significant complication during and after the procedure except gross hematuria in one patient. CONCLUSION: Because of high false positive value of TRUS, random biopsy is necessary for the diagnosis of prostatic cancer. TRUS-guided transrectal automated core biopsy is accurate and safe in patient with prostatic disease.