Extracellular nucleic acids could serve as molecular markers in the early detection of cancer and in the prediction of disease outcome. In this study we examined six molecular markers, such as: variations in the quantity of DNA in plasma, glutathione-S-transferase P1 (GSTP1) gene methylation status in plasma, carcinoembryonic antigen (CEA) and prostate-specific membrane antigen (PSMA) mRNA in peripheral blood mononuclear cells (PBMC), and plasma samples from prostate cancer patients in different stages. The combination of DNA load and GSTP1 promoter methylation status identified 83% (10/12) of the prostate cancer patients before therapy. This study shows that free circulating DNA can be detected in patients with prostate cancer compared with disease-free individuals, and suggests a new, noninvasive approach for early detection of prostate cancer.