The purpose was to investigate the relation between fluoride concentrations in whole saliva, parotid ductal saliva, and plasma in 5- to 10-year-old children (n = 17). Two stimulated whole-saliva samples were obtained from each child. Before the second sample was obtained, each child rinsed several times with a total of 100 ml of deionized water. Parotid saliva samples were obtained by use of a Lashley cup. Fluoride concentrations were determined by fluoride ion-specific electrode after diffusion with hexamethyldisiloxane. Rinsing with deionized water did not significantly reduce the fluoride concentration in whole saliva. The whole-saliva fluoride concentrations were not significantly related to those in plasma or parotid ductal saliva. Parotid fluoride concentrations, however, were significantly related to plasma fluoride concentrations (p < 0.0001) by a proportionality constant of 0.80. It was concluded that parotid salivary fluoride concentrations can be used to estimate plasma fluoride concentrations in 5- to 10-year-old children.