Objective To evaluate the influence of the cytochrome P450（CYP）3A5 genes of both donorsand recipients on the concentration/dosage ratio（C/D） of tacrolimus in adult liver transplant patients. Methods 51adult liver transplant patients received tacrolimus were included in this study. The CYP3A5 polymorphism （includingdonors and recipients） were measured at the time of transplantation，and then tacrolimus-based immunosuppressivetherapy was started on the basis of each patient's genetic constitution. CYP3A5 * 1/ * 1 genotype and  * 1/ * 3 genotypewere combined into expressor genotype and * 3/ * 3 genotype was nonexpressor group. The C/D of tacrolimus during3 months after surgery was analyzed in relation to the CYP3A5 genotype. A stepwise regression was used to analyze the relationship between C/D of tacrolimus and genotype，time course，age，liver weight in liver transplantpatients.Results C/D of tacrolimus in patients with CYP3A5 * 1 expressed donor was lower than C/D of patientswith CYP3A5 * 1 unexpressed donor（P＜0.05 or P＜0.01）； C/D in CYP3A5 * 1-carried patients was also lowerthan CYP3A5 * 1 unexpressed patients（all P＜0.01）. C/D in CYP3A5 * 3/ * 3 patients with CYP3A5 * 3/ * 3 donorwas obviously higher campared with the other 3 groups during 3 months after transplantation（all P＜0.01），andthe difference of C/D in other 3 groups was not statistically significant （all P＞0.05）.The regression equation：Y（tacrolimus concentration/dose ratio per unit weight） ＝ 1.025 + 0.625 donor genotype + 0.520 receptor genotype +0.021 postoperative length － 0.008 patients with age. Conclusions Those findings suggest that the CYP3A5 * 1genotype in donors as well as in patients both contributes to inter-individual variation in the C/D of tacrolimus in adultliver transplantation.The factors impacting patient's tacrolimus blood concentrations are donor's CYP3A5 genotype， recipient's CYP3A5 genotype，time course and age . Patients can benefit from setting and adjusting FK506 dosageaccording to CYP3A5 genotype of both donors and recipients.