Abstract The effect of radiation interception on leaf conductance and leaf water potential in six-years old lychee trees ( Litchi chinensis Sonn. cv. Bengal) was investigated during the dry season in subtropical Queensland, Australia. A high degree of exposure of leaves to direct radiation raised leaf-air water vapour concentration gradient (Δ w) and resulted in lower leaf conductance and leaf water potential. Interior leaves of the south side of trees were less sensitive to atmospheric and radiation effects and are the best indicator of drought stress in lychee. Completely random or stratified sampling is necessary to estimate a true mean value for calculation of canopy transpiration or photosynthesis.