A clinical investigation on caries attack of different dental surfaces was carried out in a high fluoride area (Campagnano) in 144 adults. At the same time the fluoride concentration of 269 samples of different dental surfaces of 65 caries-free teeth, belonging to adults from the same area, was determined. Statistical analysis of clinical and chemical data, and a comparison between these data and earlier data collected in a low fluoride area (Rieti) were carried out. Highly significant differences, both in caries susceptibility and in fluoride content, were found in Campagnano between the occlusal and the other four surfaces (the occlusal surfaces were the most affected by caries and the lowest in fluoride). In Rieti similar findings were observed in the clinical data but not in chemical data. All surfaces in Campagnano showed a significantly higher fluoride content than the surfaces in Rieti and a significantly lower percentage in caries. However, the increase in fluoride content varied for the different surfaces. Caries reduction was also not the same for different surfaces.