In 50 calcium-oxalate stone-forming patients, the total excretion of glycosaminoglycans (GAGs) and four of its subgroups [chondroitin-4-sulfate (CS-A), chondroitin-6-sulfate (CS-C), dermatan sulfate (DS), and hyaluronic acid (HY)] was investigated before ESWL and in the following 5 days. The standard value was determined by reference to a group of healthy test subjects. The excretion of GAGs was significantly higher in healthy test persons than in stone-forming patients. Twenty-four hours after ESWL administration, GAG excretion enhanced significantly but returned to normal values in the course of three days. ESWL had no influence on the proportional composition of GAG subgroups CS-A, CS-C, DS and HY. The increase in GAG excretion after ESWL indicates a transient injury of renal tissue, i.e. of the mucus layer lining the urothelium. This lesion, however, can be regarded as temporary with later restitutio ad integrum.