Background: Delayed renal function after transplantation is a strong predictor of long-term graft survival. As an increased expression of endothelin (ET) has been demonstrated during ischemia/reperfusion injury, we hypothesized that ET-A receptor blockade could improve the recovery of acute renal failure in a rat model of isogeneic kidney transplantation. Methods: Kidneys of Fisher (F344, RT1<sup>1v1</sup>) rat donors flushed with cooled University of Wisconsin solution were transplanted into bilaterally nephrectomized Fisher rats. Recipient animals were treated orally either with vehicle or the selective ET-A receptor antagonist LU135252 (30 mg/kg/day p.o.) for 14 days. Unilaterally nephrectomized Fisher rats not subjected to ischemia served as controls. No immunosuppression was given. On days 2, 6 and 14, metabolic studies were performed to evaluate endogenous creatinine clearance, fractional sodium excretion, and urinary endothelin excretion. Kidneys were harvested at the end of the experiment for determination of renal ET content and immunohistochemical assessment. Results: Urinary ET excretion was increased in vehicle-treated isografts compared to uninephrectomized controls after 14 days. Treatment with LU135252 resulted in a significant improvement in creatinine clearance and fractional sodium excretion to the level of uninephrectomized rats after 14 days. Isografts treated with selective ET-A receptor blockade demonstrated a marked reduction in cell surface markers for macrophages/monocytes, T cells, MHC-II, and ICAM-1. Conclusion: Treatment with the selective ET-A receptor antagonist LU135252 accelerates recovery of renal function after isogeneic renal transplantation and attenuates cellular graft infiltration. This effect could have major implications for the treatment of patients undergoing renal transplantation, as an improved initial renal function may delay the onset of chronic allograft rejection.