Introduction: Transrectal ultrasound (TRUS)-guided prostate biopsies using 18G calibre needles are widely used; most often 12-core tissue samples of the peripheral zone are obtained. Although the diagnostic yield of prostate biopsies is fair, there is still a potential for false negative results, which necessitates repeat biopsies. In an effort to improve the accuracy of prostate biopsies, different sampling schemes have been developed. One strategy has been to increase the number of core biopsies performed on each patient. Another strategy has been to improve the reliability of prostate biopsies using larger calibre needles, thereby increasing the amount of tissue obtained for each core biopsy. Methods: After approval by our institutional review board, we prospectively compared two biopsy needle sizes (18G vs. 16G) in relation to prostate cancer diagnosis, pain, bleeding and infection rates on 105 patients. Each patient underwent 6 TRUS-guided prostate biopsies with the standard 18G needle and 6 other biopsies with the experimental 16G needle. To evaluate possible complications related to the use of a larger 16G needle in the experimental group, we compared pain, bleeding and infection rates with a control group of 100 patients who underwent 12 biopsies with a single 18G needle (18G group). Pain, bleeding assessment and infection events were evaluated using patient questionnaires and telephone interviews. Results: TRUS-guided prostate biopsies using 16G calibre needles did not increase cancer detection or non-malignant pathology rate, including prostatic intraepithelial neoplasia (PIN) and atypical small acinar proliferatio (ASAP). Pain, bleeding and infectious complications were similar in both groups. Infection was defined as temperature above 38°C occurring within 48 hours after the procedure. We identified 4 patients with post-biopsy fever in the experimental (16/18G) group and 4 other patients in the (18G) control group. The post-biopsy infection rate is higher than reported just a few years ago and indicates that quinolone resistant Escherichia coli seems to be more prevalent in our urban setting than previously suspected. Limitations to our study include small group numbers. Conclusion: Larger 16G needles appear to be safe for TRUS-guided prostate biopsies. Further study in a larger, multi-institutional, prospective, randomized manner with 16G needles is warranted to assess the theoretical benefit of larger core biopsies in prostate cancer detection.