OBJECTIVES: The purpose of this study was to evaluate the anti-caries activity of bamboo salt on Streptococcus mutans. METHODS: The pH of bamboo salt, bay salt, and NaCl were measured at concentrations of 1%, 3%, 5%, and 10%. At 3, 6, 9, 12, 18, and 24 h, the growth and acid production of S. mutans was measured using a spectrophotometer and pH meter, respectively. RESULTS: The growth of S. mutans remarkably reduced with the addition of 1% NaCl. Bamboo salt showed effective growth inhibition at concentrations higher than 3%. Bay salt showed effective growth inhibition at concentrations higher than 5% (P<0.01). At salt concentrations of 1%, the pH value of bacterial culture broth reduced to below 5.5 after 12 h. Bamboo salt and NaCl reduced acid production at concentrations higher than 3%. Moreover, bay salt decreased acid production at concentrations higher than 5%. CONCLUSIONS: These results showed that the bamboo salt inhibited growth and acid production of S. mutans. Thus, bamboo salt can be considered a useful material for the prevention of dental caries.