Many changes in gene expression occur in response to water-deficit stress. A challenge is to determine which changes support plant adaptation to conditions of reduced soil water content and which occur in response to lesions in metabolic and cellular functions. Microarray methods are being employed to catalogue all of the changes in gene expression that occur in response to specific water-deficit conditions. Although these methods do not measure the amount or activities of specific proteins that function in the water-deficit response, they do target specific biochemical and cellular events that should be detailed in further work. Potential functions of approx. 130 genes of Arabidopsis thaliana that have been shown to be up-regulated are tabulated here. These point to signalling events, detoxification and other functions involved in the cellular response to water-deficit stress. As microarray techniques are refined, plant stress biologists will be able to characterize changes in gene expression within the whole genome in specific organs and tissues subjected to different levels of water-deficit stress.