We investigated the diagnostic yield for systematic 12-core transrectal prostate needle biopsies. Subjects were 56 prostatic cancer patients who were diagnosed with transrectal ultrasound-guided 12 core prostate needle biopsies and who underwent open retropubic radical prostatectomy. Pathological findings were compared between needle biopsy specimens and total prostatectomy specimens in terms of the presence or absence of cancer foci. For the comparison, the prostate was divided into 5 regions : the apical, middle, basal, far lateral and transitional regions. Then, based on the pathological findings of the biopsies, the sensitivity, specificity, positive predictive value and negative predictive value were calculated for each region. As a result, the sensitivity and the specificity in the transitional region tended to be lower than in other regions, and six of ten false positive lesions were located in the transitional region on the biopsy specimens. Also, the negative predictive value tended to be lower in the apical and far lateral regions. In conclusion, thorough punctures in the apical, transitional, and far lateral regions of the prostate at the systematic transrectal biopsy were paramount important for improving the detection of cancer foci in these regions.