Abstract: This study was carried out to describe physiological and morphological attributes that differentiate 12 Tunisian olive varieties cultivated in the collection of Chott Mariem (arid semi climate) in period of severe drought. Our results show that there were significant genetic differences for stomatal density, number and diameter of the trichomes peltates, length and the relative surface of stomatal pore, stomatal conductance, transpiration rate, elasticity of the petiole and for water losses from detached leaves. The classification of the various varieties according to their favorable behavior to water deficit show that 'Zarrazi' appears the most adapted to drought among the 12 studied varieties. In addition 'R'khami' appears the most sensitive variety to drought.