Water is rather scarce in the GCC countries. Therefore, every drop of water must be carefully used economically, i.e., no higher quality water should be used for a purpose that can tolerate a lower quality. As a substitute for fresh water in agriculture and industry, treated wastewater has an important role to play in the GCC countries＇ water resources management. The present gap between water demands and available water resources has led these countries to consider domestic wastewater as an integral part of their water resources. At present, GCC countries recycle no more than 35% of their total treated wastewater, which contributes 2.2% of their total water supply, being used mainly for landscaping, fodder crop irrigation, and some industrial uses. However, major plans for water recycling exist in most of these countries. The main handicaps for reuse expansion are both social (psychological repugnance and religion) and technical (microbiological pollutants, potential heavy metals accumulation in irrigated soil, and industrial waste mixing). If only 50% of domestic water supplies are treated and recycled in agriculture, recycled waters have the potential to meet more than 11% of the GCC countries total water demands, could satisfy more than 14% of their agricultural sector demands, and could reduce fossil groundwater withdrawal by more than 15% by the year 2020.