Catalase activity in peach flower buds was found to be comparatively high before winter dormancy. Chilling at 5°C resulted in a decrease in catalase activity. The lowest level was reached near the end of dormancy. Flower buds of cultivars requiring a longer chilling requirement had the greatest depression in catalase activity. The onset of 25°C temperature following a few days at 5°C delayed change in catalase activity during the next 5°C chilling period and resulted in a condition comparable to prolonged dormancy. Flower buds near the end of rest or in a post dormant rest when placed at 25°C showed a rapid increase in catalase activity. A flower bud’s ability to rejuvenate its catalase level is correlated with it’s flowering ability. Free internal O2 due to the catalase system may trigger peach flower bud development.