The radioisotopic measurement of glomerular filtration rate (GFR) has required analysis of serial blood or urine samples over several hours, and does not allow measurement of separate renal function unless separate catherterization of individual ureters is done. Gates described isotopic method for the measurement of global and unilateral GFR based on the determination by scintillation camera of the fraction of the injected dose of Tc-99m-diethylenetriaminepentaacetic acid (DTPA) present in the kidneys 2-3 minutes after its administration.We calculated GFR according to Gates' method in 58 adult patients with various levels of global renal function using Tc-99m DTPA and validated this technique by correlation with 24 hour creatinine clearance. A good correlation was observed between 24 hour creatinine clearance and GFR calculated by Gates' formula, with an r value of 0.91 (p〈0.01). We concluded that determination of GFR according to the Gates' formula allows good and reproducible prediction of GFR with great rapidity and simplicity rendering this technique suitable for clinical practice.