Greenhouses have expanded from Northern areas to very different climatic areas in the World,including arid and semi-arid regions.The main limiting factors for greenhouse cultivation in such areas are the high ambient temperatures and low humidity,typical of these regions during almost all the year,and the availability of good quality water for irrigation and cooling.Therefore,the technological options to grow in these areas are quite dependent on the average maximum temperatures along the year.If the area has average maximum temperatures not higher than 30~35 ℃ during the autumn,winter and spring months,a good choice is the combination of a plastic covered greenhouse with high natural ventilation capacity,selective shading (NIR reflection) and evaporative cooling with a fog system,provided that there is water available.During the summer months,cultivation can be moved to highlands,with cooler temperatures,using screenhouses combined with fogging (low or high pressure,depending on the water quality).If temperatures are higher than 30~35℃ during the whole year,pad and fan combined with selective shading is possibly the best option,avoiding cultivation during the summer months.Other more sophisticated technologies have been proposed for these regions,like the seawater greenhouse (limited to greenhouses close to the coast).If large greenhouse clusters are to be built near the coast,closed greenhouses could be cooled using deep-sea cold water,but technology to prevent corrosion in the collection,pumpirng and distribution systems must be developed.