tThe effects of gaseous chlorine dioxide (ClO2) fumigation on reactive oxygen species (ROS) levels andmembrane damage during storage of harvested ‘Daw’ longan fruit were evaluated. Fresh longan fruitswere collected and separated into two groups; the non-treated (control) group and the fumigated group,which were treated with 10 mg/L ClO2for 10 min. The fruits were then packed into cardboard boxes andstored at 25 ± 1◦C at RH 82 ± 5% for 7 days. ROS levels, including superoxide radical (O2•−), hydrogenperoxide (H2O2) and hydroxyl radical (OH•) increased during storage. In addition, membrane damage, asmeasured by electrolyte leakage (EL) rate, lipoxygenase (LOX) activity and conjugated diene and malondi-aldehyde (MDA) contents also increased. These increases coincided with the onset of pericarp browning.ClO2fumigation reduced ROS production and membrane damage during storage. Levels of O2•−, H2O2and OH•, EL rate, LOX activity, conjugated diene and MDA contents were all significantly lower in thefumigated group than those in the control group and were correlated with browning index. ROS increasedwith increasing membrane damage and browning. ClO2fumigation reduced the production of free radi-cals which cause membrane damage and may therefore be an effective treatment to alleviate longanbrowning during storage.©