Kidney transplantation is the most appropriated treatment in end stage renal failure patients in order to improve quality of life. However, patients have to take immunosuppressive drugs to prevent graft rejection. Tacrolimus is the most common immunosuppressive drug used now. However, tacrolimus has narrow therapeutic level and needs regularly therapeutic monitor because of inter-individual variation in dosage regimen. Not only age, body weight and drug interaction but also genetic factor in metabolic pathway of tacrolimus plays an important role in tacrolimus blood level. Previous data showed CYP3A5 genetic polymorphism was significant effect tacrolimus blood level. From previous study showed the mean dose of tacrolimus required for the induction phase was significantly higher (P= 0.006) in the CYP3A5*1/*1 group at 0.142±0.050 mg/kg/day than that required by patients who carried either the CYP3A5*1/*3 group of 0.097±0.040 mg/kg/day or the CYP3A5*3/*3 group of 0.077±0.020 mg/kg/day. Tacrolimus maintenance dose required for CYP3A5*1/*1 group of 0.12±0.03 mg/kg/day was 1.3 times higher (P<0.0001) than used for the CYP3A5*1/*3 at 0.09±0.03 mg/kg/day and 2.4 times higher than the CYP3A5*3/*3 group of 0.05±0.02 mg/kg/day. Therefore, the investigators plan to investigate a prospective study to determine the clinical outcome of tacrolimus treatment in kidney transplant recipients between genotype guided dosage regimen group and conventional group.