36Oxalic acid is an organic acid ubiquitously occurring in plants. Recently, prestorage application of oxalic acid on fruits and vegetables has received much attention. The diverse effects of oxalic acid in retardation of ripening and senescence, control of postharvest diseases, inhibition of enzymatic browning, and alleviation of chilling injury in fruits and vegetables are summarized in this chapter. The application of oxalic acid is a worthwhile strategy for some selected fruits and vegetables in relation to improvement of postharvest life and quality control during storage, and further research is required to elucidate the mechanism by which oxalic acid mediates maintenance of the postharvest viability of fruits and vegetables.