A quantitative study has been made of changes in oxygen content, ascorbic acid content, flavour and colour during the processing and storage of pasteurised and frozen orange juices. By means of a gas‐saturation procedure, the juices were canned with initial oxygen contents ranging from about 3.5% to less than 0.002%. In frozen juices stored at o° F the presence of free oxygen in the cans for at least one year permitted slow oxidative loss of ascorbic acid. In pasteurised juices stored at 86° F, oxidative destruction of ascorbic acid occurred only during the first few days, since free oxygen rapidly disappeared from the cans. Throughout subsequent storage anaerobic loss of ascorbic acid continued at a rate about one‐tenth of that in the early period. Anaerobic reactions also contributed to flavour changes in pasteurised orange juices since complete removal of oxygen failed to retard the development of stale flavour at 86° F.