The urinary excretion of sucrose, glucose, and fructose was measured in 9 healthy subjects consuming a common Italian diet and after 3 days of a low sucrose diet, in which the intake of sucrose was restricted but the other main nutrients were unmodified. After the low sucrose diet, we observed a significant drop in the average urinary excretion of sucrose, glucose, and fructose determined at four different times (8:00 and 10:00 a.m.; 3:00 and 10:00 p.m.). The average urinary excretion of fructose in the four urine samples was significantly correlated with dietary sucrose intake. We also found a significant correlation between the average urinary excretion of sucrose and dietary sucrose intake. Urinary fructose can be used as a marker of sucrose intake in dietary intervention studies aimed at studying the effect of variation of carbohydrate intake on specific cancers.