PURPOSE: To evaluate the improvement of prostate cancer detection provided by transrectal ultrasound(TRUS)-guided 12 core biopsy method compared with sextant biopsy method. MATERIALS AND METHODS: Between June 1997 and February 1999, 29 patients with pathologically proven prostate cancer in 124 patients who underwent TRUS-guided 12 core biopsy method were evaluated. They had abnormal findings in prostate specific antigen (PSA), digital rectal examination (DRE) or TRUS findings. The prostate was diffusely enlarged in all patients on DRE finding and In 15 cases(15/29, 52%), hard nodule was palpated. The average of PSA and prostate specific antigen density (PSAD) is 229.33 ng/ml (1-2280) and 9.14 ng/ml/cm3 (0.048-142.5), respectively. 12 transrectal biopsy, including 2 transition zones, was performed in both lobe. 6 biopsies were located in both base, middle and apex. Then 2 biopsies were inserted between 3 biopsies in both peripheral zone and 2 biopsies were performed in both transition zone. Each specimen was pathologically examined. The results of pathology were compared with method 1 and 2, respectively. We defined the method 1 and 2 as different sextant biopsy method. The method 1 is that cores are taken from both base, middle and apex and method 2 is that cores are taken from both base, apex and transition zone. TRUS findings were analyzed by two radiologists. RESULTS: Of the 29 patients with prostate cancer, 3 (10%) had carcinomas only in the additional regions as compared with method 1. When compared with method 2, 2 (7.0%) had carcinomas only in the additional regions. 2 patients were same in both cases. TRUS findings were abnormal in 21 cases in all patients and 20 were patients whose 12 biopsy method was not helpful. 12 biopsy method was helpful in 2/8 (25%) whose TRUS findings were non-specific and 1/21 (4.8%) whose TRUS findings were abnormal. Small low echoic lesion was seen in one patient whose 12 biopsy method was helpful, but cancer was found in other area. CONCLUSION: TRUS-guided 12 core biopsy method may be superior to sextant biopsy method for diagnosing cancer of the prostate when TRUS finding is non-specific. But, sextant biopsy method is sufficient when TRUS finding is abnormal.