OBJECTIVES: In view of concerns expressed by South African local authorities the aim of this study was to develop a model to determine whether water fluoridation is economically viable to reduce dental caries in South Africa. METHODS: Microsoft Excel software was used to develop a model to determine economic viability of water fluoridation for seventeen water providers from all nine South African provinces. Input variables for this model relate to chemical cost, labour cost, maintenance cost of infrastructure, opportunity cost and capital depreciation. The following output variables were calculated to evaluate the cost of water fluoridation: per capita cost per year, cost-effectiveness and cost-benefit. In this model it is assumed that the introduction of community water fluoridation can reduce caries prevalence by an additional 15% and that the savings in cost of treatment will be equal to the average fee for a two surface restoration. RESULTS: Water providers included in the study serve 53.5% of the total population of South Africa. For all providers combined chemical cost contributes 64.5% to the total cost, per capita cost per year was $0.36, cost-effectiveness was calculated as $11.41 and cost-benefit of the implementation of water fluoridation was 0.34. CONCLUSIONS: This model confirmed that water fluoridation is an economically viable option to prevent dental caries in South African communities, as well as conclusions over the last ten years that water fluoridation leads to significant cost savings and remains a cost-effective measure for reducing dental caries, even when the caries-preventive effectiveness is modest.