The aim of this study was to assess the effects of 1 g of mycophenolate mofetil (MMF) on T-cell function and inosine monophosphate dehydrogenase (IMPDH) activity among patients undergoing kidney transplantation. Five patients undergoing renal transplantation from a living donor were enrolled in this study. Compared to baseline (before MMF intake), CD25 and CD71 expression were significantly decreased during the first hour following MMF intake. T-cell proliferation and IMPDH activity also decreased dramatically. Thereafter, all biomarker levels increased over time. At 4 hours, CD25 and CD71 levels, as well as IMPDH activity, returned to almost baseline values, whereas T-cell proliferation remained below baseline. Intracytoplasmic IL-2 expression remained unchanged after MMF ingestions. In conclusion, administration of 1 g of MMF was associated with a transient decrease in CD25 expression in addition to a temporary dramatic decrease in both T-cell proliferation and IMPDH activity.