The I.S.O. light‐fastness grades of thirty‐two anthraquinone disperse dyes on polyester fabric have been determined. High light fastness is exhibited by the 1‐ and 1,4‐hydroxy derivatives and 1‐ or 1,4‐sub‐stituted amino derivatives possessing N‐substituted electron‐withdrawing groups. The 1‐ and 2‐methoxyanthraquinones, 2‐hydroxyanthraquinones and all the 2‐amino derivatives examined, on the other hand, have poor light fastness. The high light stability of the 1‐hydroxy‐ and 1‐anilinoanthraquinones may be due to rapid de‐activation of their photo‐excited singlet states, while the poor light fastness of the 2‐aminoanthraquinones is probably due to their ability to abst