Wheat crops produced under dryland conditions in the winter rainfall belt of South Africa are often subjected to water stress. To study the effect of water stress on the spring wheat cultivars Nantes, Palmiet and SST 66, an experiment was conducted in a glasshouse at a 15°/10°C (day/night) temperature. Three intensities of water stress (0% PEG = unstressed; 15% PEG = low stress intensity and 22.5% PEG = high stress intensity) were imposed with polyethylene glycol (PEG) 6000 during the period of anthesis to milk stage in the three spring wheat cultivars. Water stress increased leaf diffusive resistance (LDR) and decreased the relative water content (RWC) of all three cultivars. Although plants were rehydrated after milk stage was reached, leaf senescence was hastened and the kernel-filling period shortened. These effects increased with increasing stress intensities. The low stress intensity (15% PEG) did not affect grain yield, but plants subjected to the high stress intensity (22.5% PEG) had significantly smaller kernels and a 37.5% lower grain yield. Although cultivars differed in their response to stress treatments for some parameters, these differences were too small and inconsistent to be recommended for use in breeding programmes for drought tolerant cultivars.