We retrospectively investigated the relationship between postoperative renal function and operative factors. We performed (99m)Tc-mercaptoacetyltriglycine (MAG) 3 renography for 10 patients after they underwent laparoscopic nephron-sparing surgery for renal cell carcinoma in our institute from 2003 to 2008. We used serum creatinine level and (99m)Tc-MAG 3 renogram to assess the postoperative renal function, and assessed whether the findings correlated with physical and operative factors. There was no relationship between the rate of increase in creatinine level and other factors ; the % reduction determined from the preoperative and postoperative renograms showed a significant correlation with the operation time and the ischemic time. It is important to shorten the duration of operation and ischemia to preserve the renal function after laparoscopic nephron-sparing surgery.