Recently, several published reports have established that detection of donor DNA in recipient s blood can serve as a diagnostic tool of graft injury. The level of donor DNA measured as percentage of circulating cell-free donor DNA (%ccfdDNA) accurately diagnoses acute rejection with a high sensitivity and specificity, at times several months before the diagnosis by examining endomyocardial biopsies. The ability of cell free DNA to diagnose graft injury early opens a new window to re-examine markers of rejection. These markers are traditionally evaluated using biopsy results, often positive late during rejection. %ccfdDNA offers an opportunity to better characterize our analyses.