The photokinetic behavior of a naturally occurring chromene, lapachenole (2,2-dimethyl-6-methoxy-7,8-benzo(2H)chromene, Ch), has been investigated by using monochromatic irradiation in the UV and visible ranges. Two colored photoproducts were identified : one is thermoreversible, the other is thermostable and photoreversible. The quantum yields of the color-forming and color-bleaching photoreactions were determined by a spectrokinetic method. The kinetic parameters of the thermal steps were measured (285 - 325 K). The sensitized color-forming reaction was also investigated, using thioxantone as a triplet sensitizer. A plausible reaction mechanism is proposed.