In plants, excess light has the potential to damage the photosynthetic apparatus. The damage is caused in part by reactive oxygen species (ROS) generated by electrons leaking from the photosynthetic electron transport system. To investigate the mechanisms equipped in higher plants to reduce high light (HL) stress, we surveyed the response of 7000 Arabidopsis genes to HL, taking advantage of the recently developed microarray technology. Our analysis revealed that 110 genes had a positive response to a 3 h treatment at a light intensity of 150 W m(-2). In addition to the scavenging enzymes of ROS, the genes involved in biosynthesis of lignins and flavonoids are activated by HL and actually resulted in increased accumulation of lignins and anthocyanins. Comparing the HL-responsive genes with drought-inducible genes identified with the same microarray system revealed a dense overlap between HL- and drought-inducible genes. In addition, we have identified 10 genes that showed upregulation by HL, drought, cold and also salt stress. These genes include RD29A, ERD7, ERD10, KIN1, LEA14 and COR15a, most of which are thought to be involved in the protection of cellular components.