Transgenic Arabidopsis plants overexpressing the wheat vacuolar Na(+)/H(+) antiporter TNHX1 and H(+)-PPase TVP1 are much more resistant to high concentrations of NaCl and to water deprivation than the wild-type strains. These transgenic plants grow well in the presence of 200 mM NaCl and also under a water-deprivation regime, while wild-type plants exhibit chlorosis and growth inhibition. Leaf area decreased much more in wild-type than in transgenic plants subjected to salt or drought stress. The leaf water potential was less negative for wild-type than for transgenic plants. This could be due to an enhanced osmotic adjustment in the transgenic plants. Moreover, these transgenic plants accumulate more Na(+) and K(+) in their leaf tissue than the wild-type plants. The toxic effect of Na(+) accumulation in the cytosol is reduced by its sequestration into the vacuole. The rate of water loss under drought or salt stress was higher in wild-type than transgenic plants. Increased vacuolar solute accumulation and water retention could confer the phenotype of salt and drought tolerance of the transgenic plants. Overexpression of the isolated genes from wheat in Arabidopsis thaliana plants is worthwhile to elucidate the contribution of these proteins to the tolerance mechanism to salt and drought. Adopting a similar strategy could be one way of developing transgenic staple crops with improved tolerance to these important abiotic stresses.