A collective measures of oral hygiene have been carried out at monthly, quarterly and half-yearly intervals on 442 pupils at the 6th to 8th classes, integrated in rhythm of the school-year. These investigations demonstrate the general possibilities of collective preventive measures also in this group of age. By means of a well organized system of care progress will be obtained in the sense of oral health. However twicely instructed measures of oral hygiene for each school year are not sufficient, if started at first in the superior classes.