AbstractFree sterol and phospholipid in the cortical tissue of apple were determined during storage of the fruits in air at 12 and 3.5°C and in 2 kPa O2(98 kPa N2) at 3.5°C. In air at 12°C, the sitosterol content declined slightly (about 4%) during fruit ripening whilst phospholipid increased about 8%. At 3.5°C in air and 2 kPa O2, sitosterol content increased by 16% and phospholipid by 25–31%. The increase in phospholipid in 2 kPa O2occurred more slowly than in air. Transfer of apples to air after 33 or 64 days in 2 kPa O2led to rapid accumulation of phospholipid in the fruit (20% and 10%, respectively) compared with apples maintained in 2 kPa O2. An increase in concentration of phosphatidylcholine (PC) accounted for most of the change observed in total phospho