The aims of the present investigation were, first, to follow the secretion of free glucose in parotid saliva in various subjects after a single oral intake of different carbohydrates, and second, to compare the salivary glucose concentration with the concentration in blood. Twenty healthy subjects, three women and 17 men, 20-35 yr of age, participated. They were asked not to eat or drink anything from 10 p.m. the night before the examination. 75 g of carbohydrate (glucose, fructose, or sucrose) dissolved in 300 ml water was ingested the next morning at 8 a.m. One experimental series with glucose was performed in triplicate in 10 of the subjects. Approximately 1.5 ml of citric acid-stimulated parotid saliva was collected before (0 min) and 15, 30, 45, 60, and 120 min after the intake. Salivary concentration of glucose was analyzed enzymatically. Most of the 0-min samples showed a variation in glucose concentration from 5 to 25 mumol/l. After the glucose, fructose, and sucrose intakes, the salivary glucose level increased about 2-4 times, especially in the 30-min samples. A large inter- as well as intra-individual variation was found both in the 0-min samples and in the samples collected after the different intakes. The correlation between the glucose concentration in saliva and blood was higher after than before the carbohydrate intakes.