Altered urinary excretion of glycosaminoglycans (GAG) has been reported in patients with nephrolithiasis, with chronic glomerulonephritis, and incipient diabetic nephropathy, but evaluation of urinary GAG has not been reported in infections and proliferating diseases of the urinary tract. Urinary excretion of GAG was measured in 50 patients with idiopathic calcium nephrolithiasis (ICN) of whom 20 had associated urinary tract infection, in 20 subjects with recurrent infection of the urinary tract (UTI), and in 18 patients with bladder papillomatosis. Mean values were significantly lower in ICN, increased in papillomatosis, and in the normal range in UTI.