Background: Manganese superoxide dismutase (MnSOD) is a major enzyme that is responsible for the detoxification of reactive oxygen species in the mitochondria. Mitochondrial DNA damage may contribute to carcinogenesis as an important risk factor. The aim of this study was to investigate the relationship between prostate cancer and MnSOD Ala-9Val polymorphism in Turkish men with prostate cancer. Patients and Methods: Fifty patients with prostate cancer and 50 healthy controls were included in this study. Gene polymorphism was determined using a PCR-RFLP method. Results: The Ala/Ala genotype and the Ala allele were found at statistically higher frequencies in patients with prostate cancer as compared to controls (p < 0.05). The patients suffering from prostate cancer were divided into two groups according to Gleason score: aggressive prostate cancer and non-aggressive prostate cancer. It was observed that carrying the Ala/Ala genotype or the Ala allele resulted in an insignificant increase in the frequency of aggressive prostate cancer compared to nonaggressive prostate cancer. It was concluded that MnSOD Ala allele might be the cause of prostate cancer risk among alcohol users. Conclusion: The results of our study of Turkish prostate cancer patients suggest that mutation of the MnSOD gene may be an improtant risk factor for prostate cancer.