ABSTRACTAn attempt was made to assess the effect of regularly repeated professional mechanical tooth cleaning on caries development and gingivitis in schoolchildren. A total of 209 children from the first (7–8 years old), fourth (10–11 years), and seventh (13–14 years) classes of an elementary school in Sweden participated. Children from each age group were assigned to one test and one control group. At a baseline examination the state of the gingiva, the oral hygiene and the number of decayed and filled tooth surfaces were determined. Once every second week after the baseline examination the members of the test groups were given careful oral prophylaxis including topical application of monofluoro‐phosphate. Once a month the members of the control group brushed their teeth under the supervision of a dental nurse. Twelve months after the initial examination the test and control groups were re‐examined. The results show that children given frequent oral prophylaxis combined with topical fluoride applications had clean teeth, only negligible signs of gingivitis, and practically