TIM-3 is a recently described molecule specifically expressed on Th1 differentiated T cells. We explored the usefulness of urinary mRNA profiles in the diagnosis of renal acute rejection (AR). Sixty urinary samples from renal transplant recipients simultaneously collected to allograft biopsy, (AR = 30 and No-AR =30), and 12 urinary samples from stable renal transplants were analyzed. Urinary mRNA encoding for TIM-3 and IFN-gamma were quantified using real time RT-PCR. TIM-3 mRNA was highly expressed in AR (559.19 +/- 644.41) compared to No-AR (3.78 +/- 7.20), and stable transplants (0.54 +/- 0.76), p < 0.001. To a lesser degree, IFN-gamma mRNA transcripts were also increased in AR (50.40 +/- 38.71), compared with No-AR (4.69 +/- 12.62), and stable transplants (0.38 +/- 0.44) p < 0.001. The highest expression of TIM-3 in AR makes it a promising noninvasive test for its diagnosis.