The fractional renal uptake of intravenously administered Tc-99m DTPA, within 2 to 3 minutes following radiotracer arrival in the kidneys, is proportional to the glomerular filtration rate (GFR). Thus it is possible to determine total, as well as individual kidney, GFR by a radionuclide technique which needs only six minutes of patient time and requires neither blood nor urine samples. The radionuclide computed GFR correlates extremely well with 24-hour creatinine clearance determinations, and is highly reproducible. This method has been used in nearly 500 split renal function determinations and has provided valuable, accurate information.