Eligible patients will be consecutive KTRs from Necker Hospital during one year (n≈180). Urine samples will be collected at 1, 3, 6, 9 and 12 months post-transplantation, and 21 mRNAs involved in EMT/fibrogenesis and the alloimmune response will be quantified by PCR. Allograft fibrosis will be quantified by image analysis, developed in our unit. Urinary cell mRNA profiles will be correlated with data from protocol biopsies (3 months and 1 year) and glomerular filtration rate (GFR) at 1 and 3 years. Diagnostic and prognostic accuracy of mRNA levels will be determined.