A new method of combined serial scintigraphy and renography, using a scintillation camera and 99mTc-DTPA is evaluated. Renographic curves, corresponding to light-pen "areas of interest" over the renal parenchyma, were processed. "Blood-background" curves were recorded from an external detector over the temporal region of the head and also from an "area of interest" corresponding to the aorta and inferior vena cava. The uptake phase of the renogram was always linear. The sum of the slopes of the uptake phase of both kidneys correlated well with the measured glomerular filtration rate in 25 patients with renal insufficiency of various degrees. Single-kidney function estimated from the slopes correlated reasonably well with single-kidney function estimated from 131I-Hippuran renography with external detectors. The method described minimizes errors in the estimation of single-kidney function, and both anatomic and functional information is obtained.