Abstract: The invention relates to a process in which an aromatic hydroperoxide of formula: ##STR1## wherein independently R.sub.1 is methyl or ethyl, R.sub.2 is hydrogen, methyl or ethyl, or where R.sub.1 and R.sub.2 together form an alicyclic ring of 5 or 6 carbon atoms, R.sub.3 is hydrogen or alkyl and R.sub.4 and R.sub.5 are hydrogen, alkyl or together form an automatic ring, n is 0, 1 or 2 and n.sup.1 is 1 or 2, is converted to a phenol and a carbonyl compound in a catalyzed cleavage decomposition reaction. In particular cumene hydroperoxide is converted to phenol and acetone. Instead of removing the decomposition products from the reactor in the liquid phase and dissipating the reaction heat as in prior art processes the heat is used to remove the phenol and the carbonyl compound in the vapor phase leaving a liquid residue of higher-boiling compounds and catalyst in the case where a liquid cleavage catalyst is employed.