In semi-arid Mediterranean regions, perennial forage species could play a primary role in rain-fed agricultural systems by complementing the commonly used annual species in order to widen the forage utilization by animals. To identify cultivars characterized by high drought resistance and water use efficiency a greenhouse study was carried out on 3 cultivars of Dactylis glomerata L., 1 cultivar of Festuca arundinacea Schreb and 1 cultivar of Phalaris acquatica L. Net photosynthesis, transpiration rate, stomatal conductance, Relative Water Content and Specific Leaf Area were monitored during the water stress period. D. glomerata 'Ottava' showed the highest photosynthetic activity while P. acquatica 'Partenope' and F. arundinacea 'Tanit' showed the lowest transpiration and photosynthesis rates. Under drought conditions, stomatal conductance and transpiration rate were less variable than net photosynthesis. D. glomerata seemed more adapted to severe water deficit conditions since it maintained longer a high photosynthetic rate even at the most severe drought treatment.