PURPOSE: To assess the diagnostic value of an initial 24-sample transrectal ultrasound guided (TRUS) prostate biopsy protocol compared to the 10-core technique. MATERIALS AND METHODS: We retrospectively reviewed the prostate biopsy database of consecutive men undergoing prostate biopsies under local anesthesia by using the 10 (Group A) and 24 (Group B) protocols. Men were stratified according to biopsy protocol and PSA levels. Exclusion criteria were age = 75 years and PSA > 20 ng/mL. The Mann-Whitney U and Fisher's exact test were used for statistical analysis. RESULTS: Between April 2007 and August 2009, 869 men underwent TRUS prostate biopsies of which 379 were eligible for the study. Group A (10-cores) consisted of 243 (64.11%) men and group B (24-cores) included 139 (35.89%) men. The overall prostate cancer detection rate was 39.09% and 34.55% in Group A and B, respectively (p = 0.43). An overall 9.8% increase in Gleason 7 detection rate was found in Group B (p = 0.24). The high-grade prostatic intraepithelial neoplasia (HGPIN) detection rate in men with negative initial biopsies was 15.54% and 35.55% in Group A and B, respectively (p < 0.001). In patients with PSA < 10 ng/mL, the 24-core technique increased Gleason 7 detection rate by 13.4 % (p = 0.16) and HGPIN by 23.4% (p = 0.0008), compared to the 10 core technique. The 24-core technique increased the concordance between needle biopsy and prostatectomy specimen compared to 10-core technique (p < 0.002). CONCLUSIONS: The initial 24-core prostate biopsy protocol did not show any benefit in the detection of prostate cancer compared to the 10-core technique. However, it improved the HGPIN detection and the correlation between biopsy results and radical prostatectomy Gleason score in men with lower PSA levels.