The effect of simple carbohydrate intake on the state of urine saturation was studied in 44 patients with calcium kidney stones and in 28 healthy subjects. Renal excretion of calcium, magnesium and oxalate significantly increased and pH of urine decreased after an intake of 100 g glucose in stone formers and healthy subjects. In the basic conditions (before glucose administration) urine was supersaturated with calcium oxalate in stone formers (median 0.55) and healthy subjects (0.24; p less than 0.05). Carbohydrate intake caused a significant increase of the degree of urine saturation with calcium oxalate and uric acid. The degree of urine saturation with brushite and sodium urate after glucose administration did not change. These data suggest that excess of simple carbohydrate consumption may increase the degree of urine saturation with some of the compounds important in stone formation.