The preventive effect of fluorine against dental caries has been well-known for a long time. In recent years the addition of fluorine to the public water supply of communities has, therefore, become increasingly frequent. Since, however, the borderline between toxic and beneficial intake as regards the prevention of dental caries is very narrow, the average daily fluorine intake of a community must be investigated well in order to estimate whether or not there is reason to add fluorine to the drinking water and if so, what is the safe but adequate concentration. Food, together with drinking water, is the main source of fluorine for human beings. It is therefore, important to investigate the daily flourine intake derived from food. Some difficulties, especially with respect to foods of vegetable origin, arise in this field from possible fluorine pollution of the air by industries, the humidity of the climate, fluorine-containing fertilizers and pesticide residues. the type of soil in which a plant has been grown, and the methods of industrial processing and home preparation foods. Because of market variations in the fluorine contents of foods, individual food habits may additionally cause serious differences in the fluorine intake of the people in the same community.