A quantitative comparison of the decomposition rate of L-dehydroascorbic acid (DAsA) among vegetables was evaluated by measuring the amount of DAsA as a function of time by the HPLC method. Six vegetables were measured at various temperatures after almost thoroughly oxidizing L-ascorbic acid (AsA) to DAsA in the sample under ambient conditions. The rate constants ( k ) for the hydrolytic decomposition of DAsA were obtained by assuming that the reaction follows a 1storder rate law. The decomposition of the DAsA reagent in buffer solutions of various pH values was also examined for comparison among the vegetables. The activation energy of the reaction in six vegetables was obtained from the temperature dependence of k , and was found to be close to the value obtained for the DAsA reagent. The relationship between log k and pH for each vegetable was almost the same as that for the DAsA reagent in buffer solutions of different pH values. These results indicate that the pH value intrinsic to a vegetable governed the rate of hydrolytic decomposition at a given temperature.