The effect of light intensity on Sekiguchi lesion formation and tryptamine accumulation involved in light-induced resistance of rice（cv. Sekiguchi-asahi）inoculated with Magnaporthe grisea was determined by using neutral density filters（ND）. When the M. griseainoculated leaves were irradiated by ND-filtered lights from daylight fluorescent lamps, there was no difference in number of Sekiguchi lesions among attenuation rates０,２０,５０,７５and９０％. However Sekiguchi lesion development and tryptamine accumulation were enhanced with increasing the light intensity. In the dark condition（attenuation rate１００％）, however, no Sekiguchi lesion formation and low level accumulation of tryptamine were observed. This result suggested that Sekiguchi lesion development and tryptamine accumulation were photosynthesis activityand light intensity-dependently induced in Sekiguchi lesion mutant infected with M. grisea.