The effect of varying levels of ethylene on the chilling injury (CI) development and the changes in the levels of putrescine, squalene and a-farnesene of 'Tahitian' lime (Citrus latgolia Tanaka), 'Emperor' mandarin (Citrus reticulata Blanco), 'Marsh' grapefruit (Citrus paradisi Macf) and 'Valencia' orange (Citrus sinensis L Osbeck) stored at 0°C was investigated. It was found that different citrus fruits stored at 0°C had varying sensitivity to CI, and that low levels of exogenous ethylene induced earlier and more severe CI in all citrus fruits. The levels of endogenous putrescine, squalene and a-farnesene varied between fruit, and was affected by the time of exposure at 0°C and the presence of ethylene. The patterns of change indicate that loss of squalene coupled with loss of afarnesene could be involved in induction of CI.