An investigation was conducted on fluoride contamination of groundwater and its impacts on human health in a rural district of Togtoh County, Inner Mongolia Autonomous Region, China. As a result of water quality analysis, a fluoride concentration higher than 1.5 mg/L was detected in 62% of the wells for water supply and the highest value was 8.0 mg/L. Because of the extra intake of fluoride from drinking water, dental fluorosis and skeletal fluorosis became popular endemic diseases in this area. The authors carried out investigations on the occurrence of fluorosis and found that the morbidity was as high as 53%. An analysis of the regional distribution of fluoride concentration of the groundwater and that of the morbidity of fluorosis showed that high occurrence of fluorosis was accompanied by high fluoride concentration. The results from two case studies are described in this paper. One shows the distribution of the morbidity of dental and skeletal fluorosis by age group in a village where fluoride contamination is extremely severe, and the other shows an example of the remarkable effect of water quality improvement on human health in another village. The influence of chloride on the young generation was stressed.