The role of urinary glycosaminoglycans (GAGS) in calcium oxalate lithiasis is of great interest in urologic research. It has been claimed that GAGS are important inhibitors of calcium oxalate crystal growth and aggregation. The aim of this paper is to evaluate GAGS excretion and concentration in two groups of patients, calcium stone formers (with or without metabolic alteration) and a control group, to detect possible differences. The findings of this study show that significant differences exist not only in the 24-hour average excretion between stone formers without alteration and healthy subjects but also in the mean concentration values between the stone former and control groups. The same results are obtained from the 2-hour urine analysis. It is concluded that 2-h urine analyses of GAGS have the same or more practical value than a 24-h urine analysis and that the results must be expressed in terms of concentration.