PURPOSE: To compare histological outcomes in patients undergoing MRI-transrectal ultrasound fusion transperineal (MTTP) prostate biopsy and determine the incremental benefit of targeted cores. METHODS: Seventy-six consecutive patients with 89 MRI-identified targets underwent MTTP biopsy. Separate targeted biopsies and background cores were obtained according to a standardized protocol. Target biopsies were considered of added diagnostic value if these cores showed a higher Gleason grade than non-targeted cores taken from the same sector (Group 1, n = 41). Conversely, where background cores demonstrated an equal or higher Gleason grade, target cores were considered to be non-beneficial (Group 2, n = 48). RESULTS: There was no significant difference in age, PSA, prostate volume, time-to-biopsy, and number of cores obtained between the groups. A greater proportion of target cores were positive for cancer (158/228; 69.3 %) compared to background (344/1881; 18.38 %). The median target volume was 0.54 cm(3) for Group 1 (range 0.09-2.79 cm(3)) and 1.65 cm(3) for Group 2 (0.3-9.07 cm(3)), p < 0.001. The targets in Group 1 had statistically lower diameters for short and long axes, even after correction for gland size. The highest area under the receiver operating characteristic curve was demonstrated when a lesion cutoff value of 1.0 cm in short axis was applied, resulting in a sensitivity of 83.3 % and a specificity of 82.9 %. CONCLUSIONS: When a combined systematic and targeted transperineal prostate biopsy is performed, there is limited benefit in acquiring additional cores from larger-volume targets with a short axis diameter >1.0 cm.