The effect of CYP3A4*18B and CYP3A5*3 on concentration/dosage×body surface area ratios (C/D′), adverse effects and acute rejection of tacrolimus in renal transplant patients were investigated.  The CYP3A4*18B genotypes of 227 renal transplant patients were determined by PCR-RFLP method.  The differences of C/D′ ratios, adverse reactions and acute rejection were compared among all of the genotype groups treated with tacrolimus.  The frequencies of CYP3A4*18 and CYP3A5*3 alleles in renal transplant patients were 30.8% and 74.2%, respectively.  No significant association was found between the C/D′s of tacrolimus and CYP3A4*18B genotypes when they were classified by two CYP3A5 genotypes (P > 0.05).  While after the effects of CYP3A4*18B genotype were eliminated, the C/D′ ratio of tacrolimus in patients with CYP3A5*1/*1 and *1/*3 genotype group was significantly lower than those with CYP3A5*3/*3 genotype groups (P < 0.01).  There is no significant difference in adverse effects and acute rejection among different genotypes (P > 0.05).