The purpose of this prospective study (30 controls and 100 renal patients) is to compare one to each other the values of renal function measured with: 1--the DTPA 99mTc , 2--the DMSA 99mTc , and 3--the creatinine clearance. After the control values being established, correlations are done for the whole group (n = 130) between the creatinine clearance, the DTPA 99mTc clearance and the fixation rate of the DMSA 99mTc . The correlations obtained are:--Clcr Versus Cldtpa = 0,91.--Clcr Versus % Dmsa = 0,90. - Cldtpa Versus % Dmsa = 0,93. and indicate the two isotopic tests performed give similar quantitative results than creatinine clearance. Camera and computer allow to measure the separate renal function one by one, the two isotopic test giving similar values for each kidney. The results of these studies give a good concordance with the observed diseases, except for partial renal artery stenosis. The pyelic retention of DMSA 99mTc product, in condition of ureteral compression, gives a potential overestimation of this test and is a matter to debate. The extreme simplicity and facility of DMSA 99mTc procedures make this investigation accessible to any patient and give excellent morphological and functional tests. DTPA 99mTc clearances--global and separate kidney--give a more sensitive approach than DMSA 99mTc does because vascular captation , elimination rates could be focused. DTPA 99mTc procedure is to be used in patients with transplanted kidney, silent IVP kidney, contrast media contraindication or for exploring glomerular clearance without urine collection.