Fluorosis continues to be an endemic problem in Yemen. More areas are being affected by fluorosis in different parts of the country. The present study tries to study the source offluoride in groundwater of the affected areas through an analytical study of three areas in the southern part of the upper valley Rasyan, governorate of Taizin Yemen. 93 wells based on the inventory of wells in the study area, which included samples of all types of aquifers. The results of the analyzed parameters formed the attribute data base for geographical information system (GIS) analysis and final output maps. Fluoride average concentration ranges from 0.85 mg / L as a minimum value in the samples taken from Al-Dabab to 2.83 mg / l as a maximum value of the samples taken from Central region. 82.76% and 75% of the groundwater samples respectively in Central and Al-Hawban area containing fluoride concentration that exceed the WHO drinking water guidelines value of 1.5 mg/l. The sewage and other wastes are the main anthropogenic source of water contamination with natural contamination by the water_rock interaction in the studied areas, the exacerbates of the problems are the lack of proper treatment of the areas sewage, the lack of good drainage system.
