Drought and salinity are among the environmental factors that constrain agricultural productivity most dramatically. Classical breeding programs aiming to improve stress tolerance have been hampered by the multigenic nature of the trait and the seemingly scarce natural genetic variability in crop plants. Novel genetic determinants governing the function of stomata and improving the performance of plants under water shortage have been identified and show promise of application in crops. Moreover, receptors of the stress hormone abscisic acid have been characterized and their interplay with key regulatory components is being understood. A critical factor of salinity tolerance in plants is the ability to exclude Na(+) from the shoot, and the modification of specific Na(+) transport processes has yielded enhanced salinity tolerance.