The purpose of this study is to evaluate the efficacy of tacrolimus modified release formulation Advagraf® after conversion from Prograf® in stable kidney transplant patients.

Inclusion Criteria:

1. Patients received a kidney transplant at least 12 months ago prior to enrollment.
2. Patients have taken unchanged dosage of Prograf® and remained stable serum level of tacrolimus at least for 12 weeks prior to enrollment.
3. Patients have kept in unchanged immunosuppressive therapy (combination therapy) at least for 12 weeks prior to enrollment.
4. Female patients of childbearing potential must have a negative urine or serum pregnancy test prior to enrollment, and agreed to the deliberate prevention of conception during the trial.
5. Patients are considered clinically stable by observer's judgment.
6. Patients must understand the purpose and risk of participating the trial and signed on the written consent.

Exclusion Criteria:

1. Patients have previously received an organ transplant other than a kidney.
2. Patients have had acute transplant rejection within 12 weeks, or acute transplant rejection requiring antilymphocyte therapy within 24 weeks prior to enrollment.
3. Patients newly diagnosed malignant tumors after organ transplant but the patients treated completely with basal or squamous cell carcinoma of the skin are excepted.
4. Patients have a known hypersensitivity to Prograf® or tacrolimus.
5. Patients whose medical condition are able to interfere with the study objectives.
6. Patients who are at the risk of drug abuse or mental disorders or communicate difficulties with the observer.
7. Patients have been participated in another clinical trial, or treated with drugs of clinical trial within 28 days prior to enrollment.
8. Patients have been taken prohibited combination agents within 28 days prior to enrollment.
9. Patients are pregnant or lactating.
10. Patient are HIV-positive.
11. Patients are not able to keep the scheduled visit.
12. Patients whose GFR (MDRD) is in the level of <30 mL/min.
13. Patients who are at the condition of 'Creeping creatinine (defined by 20% increase within 6 months prior to enrollment)
14. Patients whose SGPT/AST and/or SGOT/ALT levels have been elevated greater than 2 times the upper value of the normal range.
15. Patients have FSGS or MPGN Type II as underlying diseases.
16. Patients are with cirrhosis