Efficacy and Safety of Once-Daily Tacrolimus in Liver Transplant Recipients (SOUL)

Inclusion Criteria: * At least one year after liver transplantation * Over 20 years old(male or female) * Patient taking tacrolimus twice daily as a maintenance therapy * Patients with Tacrolimus blood levels of 3-10 at screening * Agreement with written informed consent Exclusion Criteria: * Previously transplanted another organs other than the liver or at the same time * Diagnosed and clinically treated with acute rejection within the last 6 months * Patients who have changed the method of administering concomitant immunosuppressants or steroids within the last month * Diagnosed with cancer in the last five years \[Patients, however, who have recovered from skin cancer (squamous cell/basal cell carcinoma) or thyroid cancer, hepatocellular carcinoma without main vessel invasion or extrahepatic metastasis can be enrolled\] * Patients who have positive HIV test result * Severe systemic infection requiring treatment * At screening * White blood cell count \< 1,500/mm\^3, or platelet \< 50,000/mm\^3, or Serum-C r\> 2.0mg/dl * Liver function test(T-bilirubin, aspartate aminotransferase, alanine aminotransferase)is over 3 times than upper normal limit * Patients Taking HCV(hepatitis C virus) Therapeutic Drugs * Pregnant women or nursing mothers * Fertile women who not practice contraception with appropriate methods * Participated in other trial within 4 weeks * In investigator's judgment