Abstract:  Background:  Although innate immunity is crucial to host defense against pathogens, the extent to which innate immune mechanisms participate in the rejection of allogenic tissues in humans is unknown. We hypothesize that activation of innate immunity through Toll‐like receptors (TLRs) critically regulates the development of renal allograft rejection. We have recently demonstrated decreased acute rejection in lung transplant recipients heterozygous for either of two functional polymorphisms in TLR4 associated with endotoxin hyporesponsiveness. In the present investigation, we sought to evaluate the role of innate immune activation through TLR4, in either donor or recipient, upon the development of renal allograft rejection.Methods:  Patients and donors were screened for the TLR4 functional polymorphisms (Asp299Gly and Thr399Ile) by polymerase chain reaction (PCR) using sequence‐specific primers.Results:  The incidence of biopsy‐proven acute renal allograft rejection was significantly reduced in patients receiving donor grafts heterozygous for the Asp299Gly or Thr399Ile alleles, when compared with wild type (22% vs. 0%, respectively, p = 0.02). There was no association with recipient TLR4 allele and rejection.Conclusions:  The results suggest activation of innate immunity through TLR4 in the donor kidney contributes to the development of acute rejection after renal transplantation.