A method of estimating the 131I-hippuran clearance of each kidney during renal sequential scintigraphy is presented. The clearance rates were obtained from the elaboration of the renal histograms and of a blood curve recorded on the precordium, directly compared with the injected dose. A function simulating the progressive deformation of the radioactive bolus as kidney perfusion is impaired was introduced into the computation. The method was tested on 23 patients who underwent simultaneous determination of the clearance rate with the Sapirstein method, the results being corrected to 1.73 m2 of body surface area. The correlation coefficient r between the obtained data (the sum of the clearance rates of the two sides) and the results of the Sapirstein method was 0.89.