Respiration was depressed by 10-30% CO2 in ripening bananas, pink tomatoes and pickling cucumbers; increased by 20-30% in carrot roots and unaffected by CO2 exposure in guava, orange and onion bulb. Changes in respiration seldom coincided with changes in C2H4 evolution. Evolution of C2H4 from guavas and tomatoes was substantially reduced by all levels of CO2. However, 30% CO2, accelerated C2H4 evolution in bananas, carrot roots, cucumbers, onions and potatoes which may have been due to an early injury response.