The chemistry and kinetics of tetralin thermolysis were experimentally specified under a hydrogen pressure of 8 MPa within a wide temperature range of 350-510-degrees-C. The main products are 1-methylindane and n-butylbenzene; out of a total of 16 hydrocarbons identified in the thermolysis products, only benzene, toluene, o-xylene and naphthalene are final. The general order of tetralin thermolysis is 2. The individual orders of isomerization and hydrogenolysis are 0 and 1, respectively. A simplified kinetic model of tetralin thermolysis at the initial stage agrees well with experimental data. The tetralin thermolysis was assumed to begin with a bimolecular transformation into tetralyl and cyclohexadienyl radicals. This is consistent with the facts that the main intermediate products formed from these radicals are 1-methylindane and n-butylbenzene and that the experimentally established activation energy of the total process (59.1 kcal/mol) is close to the thermodynamically evaluated enthalpy of the proposed disproportionation.