Abstract.The levels of particular mRNAs in tomato leaves are altered in response to water stress. Certain transcripts appear as a consequence of the stress whereas others diminish in abundance. These changes were analysed by cell‐free translation of leaf RNA followed by two‐dimensional polyacrylamide gel electrophoresis of the translation products. Within 20 min of the onset of reduced leaf water potential in detached leaflets, stress‐induced mRNAs appear in the transcript population. Other mRNAs accumulate more slowly and include among theirin vitrotranslation products a prominently labelled group of polypeptides of about 18–19 kD. These transcripts are recovered from detached leaflets incubated for 2 and 8h at low water potential and from leaflets of intact plants that were stressedin situfor 10d. An additional water stress‐induced mRNA that encodes a 64‐kD polypeptide is detected in the transcript population from detached leaflets when [3H]glycine is used in place of [35S]methionine in the cell‐free translations. Among the transcripts that decline in abundance as a consequence of water stress is an mRNA that encodes the small subunit of ribulose‐1,5‐bisphosphate carboxylase. Within 2h of rewatering stressed plants, certain mRNAs that were lost from the population return and those in the 18–19 kD range that are associated with the stress