Abstract A computer video image analysis system was used to quantify changes in oxidative browning of developing ‘Redskin’ peach fruit [Prunus persica (L.) Batsch]. Oxidative browning of endocarp tissue occurs rapidly at the onset of Stage I and decreases in rate and intensity during development, with little or no browning occurring by the time endocarp sclerification begins at the onset of Stage II. Conversely, little or no browning occurs in mesocarp tissue during early development, but browning increases in rate and intensity through endocarp sclerification. In this study, net oxidative browning was correlated with net polyphenyl oxidase (PPO, EC 1.10.3.2) and peroxidase (POD, EC 1.11.1.7) enzyme activity of the tissues as quantified by image analysis of PPO and POD histochemical staining reactions. Image analysis revealed localized areas of activity within the tissue.