A preliminary report is submitted on the occurrence of dental caries in Norwegian children, during and after the World War.Dental examinations of 8,000 to 9,000 school children from different parts of Norway have been carried out each year from 1940 to 1948. It is concluded from the statistical results of the investigation that the caries frequency decreased steadily from year to year during the war. The reduction in the number of carious tooth surfaces per child from the beginning of the war to the lowest number some time after the war ended amounts to 50 to 75%.A study has also been undertaken on 600 to 700 children, 2(1/2) to 7 years old. The results in this younger group show even a greater reduction.In both groups the decrease is statistically significant.From 1946 the caries frequency has increased again in the school children as well as in the pre-school children. In both groups the increase is statistically significant.The turn of the caries curve after the war differs according to the age-group.The cause of the decrease in caries frequency during the war and the cause of the increase after the war is discussed. Based on the rationing of the various food articles our tentative conclusion is that the decrease may be attributed to the lowering in consumption of refined carbohydrates and the increase in consumption of more natural foods, i.e. protective foods. This may have resulted in an increased resistance of the teeth and a reduction in the local factors which produce decay.More detailed studies of the change in caries frequency as well as of the change in food consumption and habit of living during and after the war are necessary before a definite conclusion can be drawn. Such studies are being continued.