Some of the methods described here are in use for more than 20 years for renal function studies of patients with nephro-urologic problems as well as patients after renal transplantation. There are in general four groups of renal function studies with radioisotopes: 1) The first group comprises studies of the renal function kinetics based on the renal handling of radio-hippurate (OIH). The comprehensive renal function procedure use 131J-OIH or 123J-OIH and includes renal scintigraphy, determination of effective renal plasma flow (ERPF), fractional radio-hippurate excretion and evaluation of urinary bladder function. The introduction of computer processing for evaluating of these studies has provided a powerful tool for diagnosis of renal diseases. The method studies the renal tubular function by a combination of an in vivo/in vitro technique, since the procedure comprises renal gamma camera functional-scintigraphy and determination of renal ERPF by in vitro techniques. The combination of the results of both methods allows the calculation of the split renal effective plasma flow. The estimation of the global and the split ERPF is of considerable importance in patients with acute renal failure, hypertension or outpatients with various renal diseases. The procedure is save, simple, inexpensive and has less variations and a greater reproducibility than creatinine clearance since urine collection is not required. In addition to the evaluation of tubular function, the degree of obstruction and the bladder function can be assessed for the individual kidney by inspection or computer assisted analysis of the sequential or functional scintigrams.(ABSTRACT TRUNCATED AT 250 WORDS)