This study undertakes to determine the difference in prostate-specific antigen density values among our patients with symptomatic benign prostatic hyperplasia on one hand and symptomatic carcinoma of the prostate on the other hand and then to estimate the possible PSAD cutoff level with acceptable sensitivity and specificity for detecting CAP among patients with serum total PSA values in the “grey zone PSA” range (>4 to 10 ng/ml) who have benign digital rectal examination. The gene discussed is KLK3; the disease is benign prostatic hyperplasia.