Acyloxybenzenesulfonic acids and their alkali metal and alkaline earth metal salts are prepared by a process comprising sulfonation of a phenyl ester in the presence or absence of a small amount of a complexing agent for the sulfonating agent SO.sub.3 or chlorosulfonic acid, subsequent acylation and, if desired, neutralization to give the alkali metal or alkaline earth metal salt, and, if required, subjecting the latter to oxidative bleaching before drying.