This study was conducted to investigate fasting plasma secretin and postprandial secretin concentrations after ingestion of a protein meal or a sucrose solution in 20 healthy Korean subjects. In 12 subjects, ingestion of a protein meal, hamburger resulted in a significant and sustained increase in the mean plasma secretin concentrations, from mean fasting levels of less than 10 pg/ml to 12 ~ 16 pg/ml, and the mean plasma secretin concentrations, 9 ~ 13 pg/ml, after a rice meal increased significantly but transiently compared with mean fasting levels. The magnitude of postprandial increase in the Plasma secretin concentration after the hamburger was greater than that of the rice meal. In the remaining 8 subjects, drinking of a sucrose solution resulted also in a significant but transient increase in the mean Plasma secretin concentrations, from mean fasting levels of less than 10 pg/ml to 0 ~ 14 pg/ml which were significantly greater than that after a physiological saline. Significant increase in the plasma secretin concentration was not observed during the postprandial period after the physiological saline. It is inferred from the above results that the Plasma secretin levels increase significantly after ingestions of a carbohydrate meal as well as a protein meal in the Korean race.