Objective: This study aimed to compare debris index, pH, mutans streptococci count and dental caries indices of schoolchildren having different salivary flow rates in Kanchanaburi province, Thailand. Methods: Salivary flow was stimulated by paraffin wax chewing and the saliva was collected simultaneously in a measuring cylinder for 5 min., then calculated in term of ml/min. Salivary pH was measured using ISFET pH Meter Model IQ125 (IQ Scientific Instrument,Inc.,USA). Mutans streptococci counts were determined by the micromethod using selective MSB agar medium. The oral health status of the school children were examined by using WHO (1997) oral health examination form. Results: The study samples were 674 schoolchildren, aged 6-13 years. Their stimulated salivary flow rates ranged from 0.1-3.0 ml/min and were divided into 3 groups: normal 1.0-3.0ml/min (n=380), low 0.7-<1.0ml/min (n=155) and hyposalivation <0.7ml/min (n= 139). The significant differences in d, d+D, dmft were found between normal salivary flow rate and hyposalivation groups (p<0.05). No significant differences in DI, pH, MS count, D and DMFT values were found among different salivary flow rate groups. Conclusion: Salivary flow rates had effects on dental caries of primary dentition especially in hyposalivation group. Whereas DI, pH, the amount of MS counts and permament dentition were not affected by salivary flow rates.