The continued population growth, the contamination of both surface water and groundwater, the uneven distribution of water resources and the periodic droughts have forced the water agencies to search for new sources of water supply. Use of highly treated wastewater effluents, now discharged to the environment from municipal wastewater treatment plants, is receiving more attention as a reliable water resource. In many countries, water reuse is already an important element in water resources planning and implementation. Nevertheless, the sustainable wastewater treatment and reuse is a continuous challenge. Following, an overview is made for some of the Mediterranean countries in regards to water resources, wastewater treatment and reuse, the aim being to determine the problems associated with them and to reveal ways to promote wastewater reuse for irrigation purposes.