Wool specimens were premordanted with alum, chrome, copper, iron, or tin mordants and dyed with 18 yellow natural dyes. The dyed specimens were then exposed to a xenon-arc lamp for 5, 10, 20, 40, and 80 AATCC Fading Units. The color changes were evaluated instrumentally with a color difference meter and visually by trained observers. Color differences in CIE L*a*b*units, gray scale classifications, and lightfastness ratings were reported. Turmeric, fustic, and marigold dyes faded significantly more than any of the other yellow dyes. However, dyes applied with tin and alum mordants faded significantly more than dyes mordanted with chrome, copper, or iron. In fact, mordant affected lightfastness more than dye or length of exposure. This showed that mordant was more important than dye in predicting lightfastness of colored textiles. Consequently, to make the best decisions regarding display of a textile, museum personnel should have both mordant and dye identified.