Living-donor liver transplantation (LDLT) has been considered an alternative method for treatment of patients with end-stage liver disease. However, the characteristics of pharmacokinetics of mycophenolic acid (MPA) in patients who underwent LDLT were not clear. This study was designed to compare the pharmacokinetics of MPA and its metabolites between LDLT patients and deceased donor liver transplant (DDLT) patients after oral administration of mycophenolate mofetil (MMF). Thirteen patients who underwent LDLT and 14 patients who underwent DDLT were enrolled prospectively. All patients received oral MMF administration (1.0 g, twice daily) in combination with tacrolimus (TAC). The plasma concentrations of MPA, free MPA, glucuronide (MPAG), and acyl glucuronide (AcMPAG) was determined by high-performance liquid chromatography method. There was a wide variation in various pharmacokinetic parameters of MPA and its metabolites in patients who underwent LDLT and DDLT after oral MMF administration. Although mean MPA area under the plasma concentration time curve for 0-12 hours (AUC0-12h) of MPA and MPAG in DDLT patients were higher than those in LDLT patients, there was no significant difference between the two groups. MPA concentration at 6 hours (C6h), C10h, C12h, and MPA AUC6-12h were significantly higher in DDLT group than those in LDLT group (P < 0.05). Inversely, higher free MPA AUC0-12h and significant free MPA fraction (P < 0.05) in LDLT patients were observed in DDLT patients when compared with DDLT group. AcMPAG concentrations at 4, 8, and 10 hours and AcMPAG AUC0-12h were significantly higher in the DDLT group (P < 0.05). In conclusion, after a fixed oral dose of MMF, DDLT patients had higher enterohepatic recycling contributing to total MPA exposure compared with LDLT patients. The function of glucuronide conjugation in LDLT patients was decreased compared with that in DDLT patients. Higher free MPA AUC0-12h and a significantly higher fraction of free MPA in LDLT patients suggested that a lower oral dose of MMF may be administered for patients who underwent LDLT. © 2009 AASLD.