OBJECTIVE:: Perineural invasion (PNI) is detected in almost 20% of prostate biopsies and has been related to worse prognostic factors in radical prostatectomy (RP) specimens and lower disease-free survival rates. The aim of this study was to evaluate the importance of PNI during periods of extended prostate biopsies and to determine the value of this preoperative parameter as a predictor of pathologic findings in surgical specimens and in biochemical recurrence. MATERIALS AND METHODS:: Between 2001 and 2009, 599 prostate biopsies and their respective RP specimens were examined in our laboratory. The RP specimens were always examined completely. The mean age of the patients was 61 years, and the mean PSA was 6.4 ng/mL. The mean and median number of biopsy cores obtained was 14.4 and 14, respectively. PNI was identified in 105 biopsies (17.5%). We studied the ability of PNI in prostate biopsies to determine the tumor stage in surgical specimens and the relationship of PNI with biochemical recurrence during a mean follow-up time of 51.4 months. RESULTS:: The presence of PNI in prostate biopsies was observed in older patients (63 vs. 61 years old, P = 0.008). All of the prognostic factors determined for the RP specimens were significantly worse in patients with PNI compared with those without PNI. PNI was strongly associated with a higher pathologic stage (87% specificity, 40% sensitivity, odds ratio 4.8). Stage pT3 prostatic cancer was determined in 46 (43.8%) of 105 patients with PNI on biopsy compared to 69 (14%) of 494 patients without PNI (P = 0.01). Fifty-six (19.6%) patients had a biochemical recurrence, and PNI correlated significantly with PSA recurrence. A Kaplan-Meier analysis revealed a significant difference in recurrence-free survival between patients with and without PNI (45% vs. 53%, respectively, P = 0.021, log-rank test = 0.19). CONCLUSION:: PNI is an important morphologic preoperative predictor of the pathologic stage as well as biochemical recurrence and must always be mentioned when adenocarcinoma is diagnosed on prostate biopsies.