In this study, we have performed a specific analysis of a 236 base pair (bp) fragment of the NOS3 gene promoter region flanking the polymorphisms -786T>C and -690C>T, through DNA conformational assays (SSCP – single strand conformation polymorphism) and sequencing, determining genotypes and haplotypes, and estimating their possible association with PCa and benign prostatic hyperplasia (BPH) diseases. The gene discussed is NOS3; the disease is benign prostatic hyperplasia.