The effect of light on Cucumis leaf pigments at 1 °C has been studied. Pigment degradation is a photo-oxidative process. Kinetics of pigment degradation show a slow degradation rate (lag phase) followed by a fast one. The sensitivity to photo-oxidation corresponds to the length of the lag phase. Carotene has the shortest lag phase and is most sensitive to photooxidation, followed by xanthophyll, chlorophyll a, and chlorophyll b. The lag phase decreases at 100% oxygen and disappears after boiling. Some possible factors causing the biphasic nature of chlorophyll degradation are discussed. It is suggested that carotene plays no primary role in the protection against photo-oxidation during chilling.