ABSTRACT Background: The most common species associated with dental caries is Streptococcus mutans. Different Streptococcus mutans adhesion biotypes, SpaP A/B/C and Cnm/Cbm, with ability to predict individual caries development have recently been identified. Aim: The aim of the study was to investigate if there was a difference in growth ability of the Streptococcus mutans adhesion biotypes and their relative sensitivity to biocides such as fluoride and chlorhexidine in vitro. We also aim to compare the potency of biocides in vitro to those concentrations used in the clinic. Methods: Culturing of the Streptococcus mutans biotypes in a planktonic solution with and without fluoride and chlorhexidine. Used concentrations: 3.5-4500 parts per million fluoride and 15-500 parts per million chlorhexidine. Optical density was used to measure growth under the different conditions. Results: The tests with fluoride showed a similar dose dependent inhibition of growth for all 6 biotypes of Streptococcus mutans. The tests with chlorhexidine showed a major inhibition of growth for the concentration 62 parts per million which inhibited growth more than 500 parts per million. All biotypes had a similar proliferation pattern without any biocide present. Conclusion: All tested biotypes of Streptococcus mutans had a similar pattern of sensitivity to the different concentrations of biocides and cultivation conditions used.