Gustatory stimulation was used to collect parotid saliva in an ascending flow rate pattern. F concentration was found to be independent of rate of flow. The F level in unstimulated parotid saliva, collected before the stimulate samplings, was significantly (P less than 0.01) higher than that for the stimulated collections. It is suggested that this is an apparent increase based on the movement of water out of the lumen, which is in turn triggered by sodium reabsorption. The level of F in unstimulated saliva increased almost tenfold within one hour after the oral administration of 10 mg of F, and a significant (P less than 0.01) increase persisted even at 24 hours after administration of the dosage.