A major problem for the early diagnosis of prostate cancer is the lack of clinically useful tests for screening a preclinical and asymptomic population without resort to invasive diagnostic procedures. Recent studies have demonstrated the possibility to detect genetic alterations in plasma or serum DNA from patients with prostate cancer or other cancers. Quantification and molecular event are associated with advanced stages and circulating tumor cells. These results indicate a new approach to the early diagnosis and monitoring of prostate cancer by non-invasive screening procedures based on the analysis of genetic changes in plasma.