Dyed cotton and silk cloths are prepared by using traditional technique, to investigate the lightfastness properties of vegetable dyes. Both xenon light under controlled condition and open sunlight methods are used according to JIS. The color difference is expressed by an CIE formula based on the measurements of three stimulus values and also by JIS grade. For dyed test pieces after controlled light exposures with a Xenon Fademeter and open sunlight, both three stimulus values and JIS blue scale were estimated and the color differences between original specimens and deteriorated ones through light exposure were calculated according to CIE formula. The remarkable influences of atmospheric humidity and the character of fibric components of cloths themselves are easily observed and dyes can be classified into four groups according to the rate and the degree of their deterioration. The unique behavior of Kihada dye is also observed.