A process for the preparation of a trifluoromethylphenol or the corresponding alkoxy compound which comprises contacting a halogenobenzotrifluoride of the formula ##STR1## in which X denotes halogen,R.sup.1, R.sup.2 and R.sup.3 denote hydrogen, trifluoromethyl or a substituent which promotes the replacement of X by a hydroxyl group andY denotes hydrogen, a halogen or alkoxy, at least one of the substituents R.sup.1, R.sup.2 and R.sup.3 representing a trifluoromethyl group and at least one of them representing a substituent which promotes the replacement of the radical X by a hydroxyl group,with an excess aqueous alkali metal hydroxide in an alcoholic solution in the presence of a quaternary onium salt.