A total of 10 patients with the diagnosis of renal cell carcinoma (RCC) underwent nephron-sparing surgery between January 1990 and December 2001. Serial pre- and postoperative 99mTc-mercapto-acetyl-triglycine (MAG3) scans were obtained. To examine preoperative predictability of remnant renal function, values of remnant renal plasma flow (ERPF) predicted prior to surgery were compared with values measured postoperatively. With preoperative MAG3 data, we designed the range of interest (ROI) except for the tumor area and recalculated remnant ERPF values. Remnant ERPF values predicted preoperatively correlated significantly with the postoperatively measured values 99mTc-(196.4 +/- 69.1 ml/min/1.73 vs 171.3 +/- 72.9 ml/min/1.73 [mean +/- SD], p > 0.05, r = 0.806). MAG3 dynamic renoscintigraphy appeared useful for preoperative prediction of remnant renal function after nephron sparing surgery.