Ulinastatin reduces systemic inflammatory responses and protects organs from ischemia/reperfusion-induced injury. The aim of this study is to evaluate the effect of ulinastatin on postoperative renal function in patients undergoing robot-assisted laparoscopic partial nephrectomy. Seventy patients, aged 20 to 79 years, scheduled for robot-assisted laparoscopic partial nephrectomy will be divided into ulinastatin (n=35) and control (n=35) groups. Randomly selected patients of the ulinastatin group are given ulinastatin. In contrast, patients in the control group receive an equivalent volume of normal saline as a placebo. The primary endpoints are postoperative renal function measured by serum creatinine, cystatin C, and urine output.