Bibliography: leaves 69-78. Leaf gas exchange (LGE) of mango cultivars Kensington, Irwin and Tommy Atkins was investigated in a series of field experiments under varying environmental and physiological conditions in the Ord River Irrigation Area, Kununurra, Western Australia. The environmental influences on mango during fruit development are extreme producing high vapour pressure deficient (VPD) and photosynthetic photon flux density. This combined with internal pressures associated with crop load and water stress have a profound effect on LGE. Diurnal changes in atmospheric and leaf temperature are accompanied by changes in VPD in the field. Differences in cultivars in LGE response to changing environmental conditions were significant, with Kensington appearing the most sensitive to extreme atmospheric conditions. There appeared to be no cultivar differences in LGE with changing soil moisture status.