There are concerns that the consumption of unfluoridated bottled and tank water may put children at increased risk of developing caries. OBJECTIVES: The aim of this study was to investigate the relationship between nonpublic water consumption (either from bottles or rainwater tanks) and socioeconomic status (SES) and both deciduous and permanent caries experience. METHODS: A random sample of children enrolled in the School Dental Service of South Australia participated in the study (response rate = 71.8%, n = 9988). RESULTS: Forty-five per cent of children had greater than 50% lifetime consumption of nonpublic water while 36% of children had 0% lifetime consumption. Increased use of nonpublic water occurred for children from lower socioeconomic groups, two-parent families and children from nonmetropolitan areas, with these results most likely a result of the residential location of the children. Multivariate modelling revealed a significant positive relationship between deciduous caries experience and consumption of nonpublic water, even after controlling for the age and sex of the child, SES and residential location. This relationship was significant only for those children with 100% lifetime availability of fluoridated water. The effect of consumption of nonpublic water on permanent caries experience was not significant. It is postulated that these findings may result from the lower caries activity in the permanent dentition of children aged 10-15 and possible dietary confounders. CONCLUSION: Recommendations are made for the addition of fluoride to bottled water, especially with regard to the oral health of younger children.