In order to discuss quantitative hydrogen-transfer process, cracking of benzyl phenyl ether (BPE) and dibenzyl ether (DBE) in tetralin using highly dispersed catalyst precursors such, as Fe(CO)5, MO(CO)6, and Ru(acac)3 was carried out at 648 K under a hydrogen atmosphere. Identified products from cracking of BPE were benzene, toluene, phenol, diphenylmethane, 1,2-diphenylethane, isomeric (hydroxyphenyl)phenylmethanes, benzyltetralins, and benzylnaphthalenes, and identified products from DBE were benzaldehyde and benzyl alcohol in addition to the above substances except phenol. The required amount of hydrogen to stabilize free radicals from BPE was in good agreedment with the amount of hydrogen transferred from tetralin and gas phase. In the absence of a catalyst, more than 90 mol % of hydrogen was transferred from tetralin. In the presence of Mo(CO)6-S, the amount of hydrogen transferred from tetralin decreased to around 15 mol % of hydrogen and the amount of hydrogen transferred from the gas phase increased to around 85 mol % of hydrogen required for stabilizing free radicals. Similar observation was obtained in the reaction with DBE without or with added catalysts. In the reaction of BPE or DBE in tetralin, hydrogenation of naphthalene to tetralin did not occur or occurred slightly even with active catalysts. The direct hydrogen transfer from molecular hydrogen to radicals occurred in the cracking of BPE and DBE with active catalysts such as dispersed Ru or Mo.