We investigated the association of prostate cancer (PCa) and benign prostatic hyperplasia (BPH) with genetic polymorphisms in prostate-specific antigen (PSA) (-158 G/A) and 17-hydroxylase (CYP17) (-34 T/C) genes in a Turkish population. In this study, we investigated the distribution of these polymorphisms in 148 PCa patients, 136 BPH patients, and 102 healthy individuals as controls. The polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism assay. Genotype and allele frequencies were calculated, and their associations with PCa or BPH risk are assayed. The frequency of PSA gene GA and GG genotypes was significantly higher in PCa patients than in controls (p = 0.017 and p = 0.019, respectively). GG genotype was also associated with BPH (p = 0.033). In a case analysis, according to Gleason score, the association of PSA gene GG genotype with Gleason score >7 was near to statistical significance (odds ratio, 2.94; 95% confidence interval, 0.95-9.28). There was also an association between CYP17 polymorphism and BPH (p = 0.004). No association was observed between PCa and CYP17 gene polymorphism. These data demonstrate that PSA gene promoter variation may play a significant role in the development of PCa and BPH, and that CYP17 gene polymorphism may be associated with BPH in the Turkish population studied.