Objectives: To evaluate the changes in split renal function after retroperitoneal laparoscopic partial nephrectomy with renal hypothermia using ice-cold saline. Methods: From June 2002 to October 2009, 32 patients (median age 56 years) underwent retroperitoneal laparoscopic partial nephrectomy with hypothermia using ice-cold saline for the treatment of small renal tumors. The total renal function was monitored using the estimated glomerular filtration rate. Split renal function was evaluated using technetium-99m dimercaptosuccinic acid renal scintigraphy preoperatively and 3 months postoperatively. Results: The median renal ischemic time, including the initial 10 minutes for cooling, was 52 minutes (range 28-101). Of the patients whose renal temperature was monitored, the lowest renal temperature during cooling was 15-25°C. The median decrease in the estimated glomerular filtration rate was 7.2 mL/min/1.73 m2 (range -16.3 to 33.7). The median decrease in the contribution of the affected kidney to global renal function was 5.3% (range 0.4%-21.1%). On multivariate analysis, a shorter ischemia duration was an independent predictor of a lesser decrease in the contribution of the affected kidney (P = .0032). Conclusions: The methods we have described are simple and effective to facilitate suboptimal hypothermia. The decrease in the renal contribution of the affected kidney appeared to be minimal, although the ischemic time was relatively longer in our series.