Cyclosporine (CsA) and tacrolimus (TAC) are immunosuppressant drugs characterized by a narrow therapeutic range and high pharmacokinetic variability. The effect of polymorphisms in genes related to the metabolism and transport of these drugs, namely , , and genes, has been evaluated in diverse populations. However, the impact of these polymorphisms on drug disposition is not well established in Latin American populations. Using ® probes, we determined the allelic frequency of seven variants in , , and in 139 Chilean renal transplant recipients, of which 89 were treated with CsA and 50 with TAC. We tested associations between variants and trough and/or 2-hour concentrations, normalized by dose (C /D and C /D) at specific time points post-transplant. We found that carriers required lower doses of TAC. In TAC treated patients, most carriers presented higher C /D and a high proportion of patients with C levels outside the therapeutic range relative to other genotypes. These results reinforce the value of considering genotypes alongside therapeutic drug monitoring for TAC treated Chilean kidney recipients.