From use of 99mTc-Ca-Sn-gluconate in patients with various degrees of renal failure the following conclusions were drawn: 1. a good relationship exists between the parenchymal and vascular patterns in scintigraphy and the functional renal impairment; 2. the morphological definition is good, since in most cases a differential diagnosis can be made between diffuse parenchymal disease and space-occupying lesions even very low glomerular filtration rate values; 3. this technique is supplementary to i.v. pyelography in patients with relatively good glomerular filtration rate values and is a reliable alternative to i.v. pyelography in those with low creatinine clearance values.