Objective: To investigate nephroprotective effects of a mixture of 8 L-amino acids on renal ischemia-reperfusion injury and its effects on renal endothelin-1 (ET-1). Methods: The mixture of 8 L-amino acids includes glycine, alanine, threonine, serine, valine, leucine, isoleucine and proline. Acute ischemic renal injury was induced by clamping renal pedicle for 45 minutes in rats. Sixty male Sprague-Dawiey rats were randomly divided into 3 groups: a sham-operated group ( Group A, n = 8), a control group (Group B, n = 26 ) and an amino acid- treated group (Group C, n = 26 ). Amino acids were infused at a rate of 1 mi · 100g-1 · h-1 I hour before ischemia and during 3 hours of the whole reperfusion. The serum creatinine values, BUN levels, creatiulne clearance, urine sodium & potassium excretion, urine lactate dehydrogenase (LDH),the rate of urine flow and histological examination were measured. Renal ET-1 levels were assayed with radioimmunological assay (RIA) Results: The creatinine clearance was 471.0 μl/min ± 121.5 pi/main in Group C and 227.0 μl/min ± 27.0 μl/min in Group B 3 hours after reperfnsion, P ＜ 0.01 ). The urine flow rate was 63.6 pi/min ± 15.2 μl/min in Group C and 24.3 μl/min ± 7.7 μl/minin Group B, P ＜ 0.01 ) 1.5 hours after reperfusion. The serum creatinine was 85.0 μl/min ± 7.7 μmol/L and BUN oncentration11.4 mmol/L ±3.9 mmol/L in Group C and 112.7 μmol/L ± 19.5 μmol/L and 20.7 mmol/L ± 6.6 mmol/L respectively in Group B after 24 hours of reperfusion (P ＜ 0.05) . The mean histological score by standards of Paller in kidneys was 108.7 ± 15.7 in Group C, and 168.8 ± 14.8 in Group B (P ＜ 0.01 ). The renal ET-1 levels 15 minute and 3 hours after reperfusion were 7.2 pg/mg ± 0.8 pg/mg and 9.6 pg/ml ± 1.0 pg/ml in Group C , and 10.1 pg/ml ± 2.8 pg/ml and 13.0 pg/ml ± 2.7 pg/mi in Group B ( P ＜ 0.01). Conclusions: The mixture of 8 L-amino acids can provide remarkable protection against renal isehemia- reperfusion injury in rats. This may associate with attenuation of renal ET-1 disorder.