Abstract: Objective To evaluate the protective effects of Ulinastatin on the peri-operative liver and renal function in patients undergoing cardiac surgery for tetralogy of Fallot (TO F). Methods Thirty-eight patients with TOF were divided into Ulinastatin group and control group according to admission sequence, 19 cases in each group.For Ulinastatin group, intravenous Ulinastatin was given with a dosage of 10 000U /kg at 1h before operation, 1h and 24 h after operation. For control group, no Ulinastatin was given. 10 ml fresh urine and 2 ml blood samples were collected before operation, and postoperative 1h, 10h, 24h, 48h and 72h, respect ively. The liver and renal functions were measured. Fluid intake, urine output, chest drainage, dosage of furosemide, durations of mechanical ventilation and intensive care unit ( ICU ) stay were recorded. Results Neither arrhythmia nor low cardiac output syndrome occurred for both groups. No peri-operative death. Compared with control group, dose of furosemide, period of mechanical ventilation were lower, while urine output was higher in Ulinastat in group; the aberrant climax value of urine pro tein and N-acetylglucosam inidase (NAG) were lower in Ulinastatin group (10h post-operat ively, urinem icroalbum in: 65. 2 ± 58. 3mg/L vs. 71. 8 ±58. 9mg/L ; urine transferrin: 5. 8 ± 3. 6mg/L vs. 7. 4 ± 5. 4mg/L ; urine immunoglobulin G: 26. 9±20. 3mg/L vs. 31. 3±23. 3mg/L ; 1h post-operat ively; urine NAG: 61. 4±81. 6U /L vs. 76.1±48. 5 U /L ; P lt; 0. 05) and maintained in shorter period (P lt; 0. 05) , it returned to baseline value at 48h and 72 h post-operatively. The value of alanine aminotransferase (ALT) significantly increased post-operatively at every time points in control group (P lt; 0. 01) , w hile no obvious change in Ulinastat in group (P gt; 0. 05). The increased value of aspartate aminotransferase (AST ) in Ulinastatin group was significantly lower than that in control group (10h post-operat ively: 144. 4±20. 8U /L vs. 202. 7±74. 1U /L ; P lt; 0. 01). The value of AST returned to baseline value at 48h and 72h post-operat ively. Conclusion U linastatin is an effect ive strategy for protecting peri-operat ive liver and renal function of the patients with tetralogy of Fallot and the clinical application of Ulinastatin is safe and effective.