This study was undertaken to evaluate the usefulness of transperineal mapping biopsy of the prostate as a staging procedure in the appropriate selection of patients for treatment with focal cryoablation. Between October 2001 and January 2006, a total of 80 patients underwent extensive template-guided transperineal pathologic mapping of the prostate (3-DPM), in conjunction with repeat transrectal ultrasound (TRUS)-guided biopsies. Before 3-DPM was performed, the following clinical variables were recorded: age, prostate-specific antigen (PSA), percent free PSA, total prostate volume, transition zone volume, Gleason score, TNM stage, number of positive cores, and maximum percent of positive cores. Results of 3-DPM were compared with those of TRUS-guided biopsies to determine patient suitability for focal cryoablation; this served as the study end point. Of 80 study patients, 43 (54%) were deemed unsuitable for focal cryoablation. When compared with 3-DPM in assessing patient suitability for focal cryoablation repeat TRUS-guided biopsies yielded a false-negative rate of 47%, a sensitivity of 54%, and a negative predictive value of 49%. None of the pre–3-DPM variables correlated significantly with patient suitability for focal ablation. Treatment selected by the 80 study patients included total gland cryoablation (30%), expectant management (23%), radical prostatectomy (18%), focal cryoablation (11%), external irradiation (10%), brachytherapy (6%), and combined external irradiation and brachytherapy (1%); 1% were undecided about treatment selection. In this study, we demonstrated that 3-DPM (1) effectively excluded patients with clinically significant unsuspected cancer outside the area destined to be ablated, (2) appeared to do so more effectively than repeat TRUS-guided biopsies, and (3) was able to precisely locate the site of the cancer to be selectively ablated.