Objective To compare the impacts of different beverages on plaque pH of caries-sensitive and caries-free children and to evaluate the applicability of in situ pH measurements in human dental plaque using Beetrode microelectrode. Methods The subjective population consisted of 20 children（aged 3-5 years）. Ten of them were caries-free（dmft=0）; the other were caries-active（dmft>4）. The dental plaque pH were measured in situ with a pH microelectrode within 1 h after drinking three different beverages respectively. Then the resting pH value（pHrest）, minimum pH value（pHmin）, the range of the pH（△pH） was analyzed by ANOVA. Results There was a significant difference in pHrest between caries-free and caries-sensitive children. All the pH responses in the plaque following drinking three different beverages showed a classic Stephan-type response. The differences of the pHmin, △pH in sound sites were no statistic significance（P>0.05） after drinking beverages in caries-free children. However the changes in the caries-sensitive group were more pronounced than the non-caries group. There were significant differences on the pHmin, △pH among different beverages（P
