In a 3-year clinical trial the effect of daily supervised toothbrushing with a dentifrice containing sodium fluoride/silicon dioxide and a dentifrice containing sodium monofluorophosphate/calcium phosphate and calcium carbonate was investigated. Initially about 400 children aged 9-11 years from one school in Malmö took part in the study. They were randomly divided into two groups. Each group brushed their teeth daily in school under the supervision of a dental hygienist. The children and their families were given the corresponding dentifrices for home use. The children were examined for caries at the start of the study and again after an interval of 1 year by the same dentist and according to the stated criteria. A comparison of the caries increments in the two dentifrice groups revealed a statistically significantly lower caries increment during the 2nd and 3rd experimental years in the sodium fluoride dentifrice group compared with the sodium monofluorophosphate dentifrice group.