Abstract: Objective To investigate the association of CYP3A5 and MDR1 genetic polymorphisms with the concentration/dose (C/D) ratio of tacrolimus for the feasibility of individualized medication. Methods The concentration of tacrolimus was detected by enzyme-multiplied immunoassay technique, and was adjusted by weight and dosage to C/D ratios. The single nucleotide polymorphisms of CYP3A5 A6986G and MDR1 C3435T, G2677T/A, T1236C were determined by TaqMan^® RT-PCR.The differences of C/D ratio were compared among all of the genotype groups. Results There were 5 cases with CYP3A5*1/*1, 22 cases with CYP3A5*1/*3, and 33 cases with CYP3A5*3/*3. The C/D ratios of the patients with at least one CYP3A5*1 allele (130.40±53.94) was significantly lower than those with CYP3A5*3/*3 (198.12±90.80) (P<0.01). For MDR1, there were 22, 23 and 15 recipients carried C/C, C/T and T/T respectively in C3435T, and 8, 32 and 20 recipients carried T/T, T/C and C/C respectively in T1236C. The carriers with G/G, G/T, G/A, T/A, T/T were 9, 24, 5, 8 and 14 respectively in G2677T/A. No significant difference was found in the C/D ratios of tacrolimus among different MDR1 genotypes. Conclusions Determination of CYP3A5 genotype could help individualize tacrolimus dose regimen prospectively. The patients with CYP3A5*3*3 require less dose of tacrolimus to reach the same concentrations comparing with the patients with at least one CYP3A5*1 allele.