Background: Studies have shown that alterations of steroid hormone metabolism, particularly involving testosterone, affect the risk of prostate cancer. Therefore, genetic variation in genes of enzymes which are involved could be of importance. The gene most interest is CYP17, whose enzyme product has an essential role in testosterone hormone synthesis. Some studies have indicated that the A2 allele polymorphism of CYP17 associated with increased risk of prostate cancer that could be affected by ethnicity. Therefore, the aim of this study was determination of presence or absence of the A2 allele in patients with prostate cancer. Materials and Methods: We studied the association of A2 allele and prostate cancer among 74 patients with prostate cancer and 128 healthy men which were referred to hospitals of SBMU. Results: This study revealed a significant association between prostate cancer risk and the A2 allele in an Iranian population so that A1A2 and A2A2 genotypes were more common in cases than controls with P-values of 0.029 and 0.010, respectively. Conclusions: Results of our study support a possible role of the A2 allele in sporadic prostate cancer development in Iran, in line with findings elsewhere.