Abstract: Abnormality of groundwater chemistry is a worldwide environmental issue. Longterm digestion of groundwater with abnormal chemical components adversely affects human health, resulting in various endemic diseases. Arsenicosis and fluorosis are typical endemic diseases in China. High As groundwater and high F- groundwater are the primary causes for these diseases, respectively. Those groundwaters occur in aridsemiarid inland basin with the special hydrogeochemical conditions, where the groundwater flow is very slow and the evaporation is strong. The waters, mainly HCO3Na type, are weak alkaline. Concentrations of As and F- are major factors controlling prevalence rates of arsenicosis and fluorosis, respectively. Besides, other groundwater components, habitant nutrition and diet are related to the incidence of the endemic diseases. Since little is known concerning pathogenesis of the diseases, intermultidiscipline studies should be carried out to fix the issues.

Key words: arsenicosis, fluorosis, arsenic, fluoride, hydrogeochemistry