We observed glucose metabolism and insulin secretion in healthy young men after intake of large amounts of sugar. Ten subjects, with the randomized cross-over design, ingested sucrose or maltose solution hourly from 10:00 to 13:00 (75 g in 225 ml water per time). Plasma concentrations of glucose, insulin and c-peptide were measured in fasting, at 30 min after each intake and at 2 hr after last intake. Plasma glucose concentration increased after the first intake and decreased to the fasting level from the second intake. Plasma insulin and c-peptide concentrations increased from the first intake and retained throughout following intakes. Plasma concentrations of glucose, insulin and c-peptide were higher in maltose group than in sucrose group and the significant differences were observed after the last intake. In the present study, glucose concentration maintained in the normal range after intake of large amounts of disaccharide and insulin secretion responded well to this repeated intake of disaccharide, however, maltose tended to induce insulin resistance compared with sucrose.