Photochemical conversions of O-acyl derivatives of 1-hydroxy-2-methoxy-9,10-anthraquinone have been studied by low temperature and pulsed photolysis. Acyl group structure has a substantial effect on the rate of thermal migration. Replacement of methyl by ethoxy decreases the rate constant by two orders of magnitude; replacement by diethylamino reduces it nearly five orders of magnitude. The log rate constant of the aroyl rearrangement is linearly dependent on the electrophilic constant of the substituents in the phenyl nucleus of the migrant.