The objective of this study was to investigate the effect of different water availability on the main agronomic characteristics in several cultivated sunflower inbred lines and other inbred lines obtained by a divergent selection for physiological traits starting from a wild species (Helianthus argophyllus T&G). The trial was carried out at the Experimental Farm of the University of Udine, during 1996 under rain-out shelter conditions and during 1997 in the field. At incipient flowering of the crops, water stress was imposed and maintained until physiological maturity. Of the genotypes examined, L28, which was selected as the plus variant of the wild population for gas exchange and tissue hydration, had the highest water use efficiency. (WUE), the best drought susceptibility index. (S), and an increased harvest index, (HI) under drought conditions, Genotype differences in S were mostly attributed to adjustments in the number of filled seeds per head and not to individual seed weight, in a late drought period. The results obtained indicate that high HI values under drought, which are closely related to dryland yield under field conditions, in the presence of genotypic variability should be a selection criteria to breeding for drought resistance. The lack of correlation between S and seed yield potential indicated that a high level of drought resistance and high yield potential may be combined in improved sunflower cultivars.