On two occasions, 12 adults collected unstimulated saliva and then eight samples of saliva over a 20-min period while chewing 3 g of either Wrigley's Spearmint sucrose-containing gum (SCG) or sugar-free gum (SFG) at 70 chews/min. The flow rates peaked initially, then fell with duration of stimulation. With the SFG they were slightly but significantly higher than with the SCG after 4 min of chewing. The sum of the concentrations of cations minus the sum of the concentrations of anions was not significantly different from zero for saliva elicited by the SCG. However, for unstimulated saliva and that elicited by SFG, there was a slight positive anion balance. A second series of saliva collections with SCG and SFG was made by the same 12 participants and these samples were analysed for lactate. For these collections the flow rates with SCG were not significantly less than with the SFG. The lactate concentration in saliva elicited by SCG peaked at 1.82 mmol/l in samples collected over 8-15 min, whereas samples of saliva elicited by SFG had a mean lactate concentration of 0.21 mmol/l. Of the lactate formed during the metabolism of sucrose by the oral bacteria, only 2% or less appeared to be derived from the metabolism of micro-organisms free in saliva, the balance presumably being formed in dental plaque and entering the saliva by diffusion. All saliva samples were supersaturated with respect to hydroxyapatite but stimulated saliva was significantly more supersaturated than unstimulated saliva.(ABSTRACT TRUNCATED AT 250 WORDS)