To clarify that tacrolimus-sparing regimen with minimal tacrolimus dose together with mycophenolate sodium dose increment will preserve renal allograft function without rising adverse effects

Primary endpoints:

1. estimated GFR (MDRD equation) 12 months after randomization
2. estimated GFR change from randomization to end of the study (calculated by MDRD equation and Nankivell equation)

<Inclusion criteria>

1. The patients between the ages of 20 and 75 years who received kidney transplantation one to five years prior to the study.
2. Taking tacrolimus and corticosteroid, with or without additional purine synthesis inhibitor within the recent 3 months
3. Patients with serum creatinine (sCr) level ≤ 2.0 mg/dL and variation of sCr < 30% for recent 3 months
4. Patients with urine proteinuria/creatinine ratio (PCR) ≤ 1 g/g, or 24 hour urine protein ≤ 1g/day for recent 3 months
5. Patients who provided informed consent.

<Exclusion criteria>

1. Patients who received combined non-renal transplantation, multiple kidney transplantation or re-transplantation
2. Patients whose graft from non-heart beating cadaveric donor
3. graft from HLA-identical living related donor
4. ABO blood group incompatible donor or HLA desensitized recipients
5. Patients with hypersensitivity history to mycophenolate sodium, mycophenolate acid, or mycophenolate mofetil, or to any other excipients
6. Patients with hypoxanthin e-guanine phosphoribosyl-transferase such as Lesch-Nyhan syndrome and Kelley-Seegmiller syndrome
7. Patients with history of disease which could affect absorption of study medication (e.g. diabetic gastropathy, previous gastrectomy)
8. Patients with positive serologic test results, in recipient or donor, for human immunodeficiency virus, hepatitis B or C virus
9. Patients with liver function test abnormality (alanine aminotransferase, aspartate aminotransferase, or total bilirubin > 3 times from upper normal limit), neutropenia (absolute neutrophil count < 1,500/uL or white blood cell count < 2,500/uL), or thrombocytopenia (platelet < 75,000)
10. Patients with history of cancer within 5 years, except for successfully treated localized non-melanocytic skin cancer
11. Patients who were either pregnant, lactating, planning to become pregnant in the next 12 months
12. Patients who taken medicine from other trial within 30 days.