Background: Two recent randomized clinical trials-Fixed Dose Versus Concentration Controlled and the Apomygre-evaluating the benefit of therapeutic drug monitoring of mycophenolate mofetil (MMF) in renal allograft recipients reported conflicting results. In both studies, target mycophenolic acid (MPA) AUC(0-12h) ranges (le, values used to guide MMF dosing) were derived from a previous study establishing target MPA AUC(0-12h) ranges in cyclosporine-treated patients between 30 and 60 mg/L . h(-1). Both studies found an association between MPA exposure and acute rejection. However, only one of the studies found concentration-controlled MMF dosing to be significantly associated with less biopsy-proven acute-rejection episodes compared with fixed dosing. No reduced incidence of MMF-related adverse events (AEs) was observed in either of the 2 trials when MMF concentration-controlled and fixed dosing were compared.