Peripheral blood and urine samples will be collected monthly during 1 year with informed consent from kidney transplant patients with diagnostic of CAN confirmed by biopsy. As Control Group, stable long-term transplant patients (more than 12 months post-TX) with creatinine levels <1.6 mg/dL, and proteinuria less than 500mg/24hs, will be studied. (You may want to give an estimated number of patients to be included in the Control Group) All practices dealing with human subjects will be performed according to the ethical guidelines of the Institutional Review Board for the Protection of Human Subjects of the Virginia Commonwealth University.