SUMMARYFour-and five-year-old 'Merrill Sunda~ce' peach trees, protected from rainfall by polyethylene film covers, were fully irrigated using micro-sprinkler (irrigatio~scheduling based on a tensiometer technique), or subjected to water stress at different phenological stages of fruit growth. Water deficit imposed during the first phase of rapid growth significantly increased fruit size at harvest during two experimental years when compared with the control full-irrigation treatment, while smaller fruits were produced from trees receiving an imposed water deficit during the final accelerated fruit growth, or throughout the fruit development period. When water deficit was applied to the trees during the pit hardening phase and the first two phases of fruit development, fruit size was not affected. However, shoot extension growth and limb diameter increases were limited whenever water supply was restricted. After-effects on limb expansion growth and benefits of water stress on fruit growth were obvious during the post-stress period. Moreover, premature fruit drops after the June-drop were reduced for all the water stress treatments. The level of total soluble solids was higher in fruits from the trees subjected to water stress during the final rapid phase of fruit growth, and flower bud production was improved on trees given a restricted supply of water during the critical period of flower bud induction.