The sucrose concentrations in saliva and the pH values of dental plaque were determined after a rinse with 0.6 mol/l sucrose in 10 subjects. The sucrose concentrations in saliva at 1 and at 5 min were significantly (p < 0.05) correlated to the hydronium ion concentration in the plaque material at 20 and 30 min after the rinse. A similar relationship was found between the sucrose concentration at 2 min and plaque hydronium ion concentration at 20 min, and between the sucrose concentration at 10 min and the plaque hydronium ion concentration at 30 min. It was concluded that factors influencing the early phase of salivary sugar clearance have an effect on the extent of the subsequent increase in the hydronium ion concentration in dental plaque, and thus may be important determinants in dental caries.