Application of acetaldehyde (AA) at 90 to 360 mm to intact grape berries (Vitis vinifera L. cv. Sultanina and Vitis vinifera L. cv. 103) caused an increase in CO2 production rate and a reduction in ethylene evolution rate. The increase in CO2 production rate was accompanied by a decrease in juice acidity without any change in the total soluble solids content. Addition of ACC to berry halves dramatically increased ethylene production, which was inhibited by AA. Ethanol, applied at the same concentrations as AA, neither caused a reduction in ethylene evolution nor inhibited the conversion of ACC to ethylene. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).