Zucchini squash ( Cucurbita pepo L. cv. Romanesco) were stored 19 days at 5°C in 21% ± 1% O 2 plus 0.0%, 2.5%, 5.0%, or 10.0% CO 2 and then stored an additional 4 days at 13° in air. High CO 2 levels inhibited the rate of CO 2 production and reduced the development of chilling injury symptoms at all three maturities (16, 20, and 22 cm fruit). There was a high negative correlation between CO 2 levels and reduction of chilling injury. At the end of the 23-day storage period, 82% of the 22-cm squash held in 10% CO 2 appeared salable, but they had a slight off-flavor and were soft; 79% of the fruit held in 5% CO 2 were salable, firm, and free of off-flavors; samples from 2.5% CO 2 and air were unacceptable because of decay and pitting. The percentage of unsalable fruit increased from 16- to 20-cm squash. Carbon dioxide concentrations around 5% may be useful for storing zucchini squash at about 5°, a temperature that normally causes chilling injury in zucchini.