The effect of chronic consumption of sucrose, xylitol and fructose on lipid, carbohydrate and urate metabolism was studied in conjunction with a clinical trial on the effects of these sugars on dental caries. No consistent differences were found in serum triglycerides, glucose, insulin, urate, lactate, or pyruvate concentrations or in the urinary excretion of urate between the groups using sucrose, fructose or xylitol as the dietary sweetener. Serum cholesterol tended to be lower in the fructose than in the xylitol group, but the difference disappeared when subjects with initial high serum cholesterol in the baseline examination were excluded from the calculations. The results suggest that the effects of peroral fructose and xylitol on the metabolic parameters studied in this investigation do not differ from that of sucrose.