When anthracene and tetralin are heated together at 1 atmosphere pressure in the presence of a palladium catalyst, a 30% yield of 1,2,3,4-tetrahydroanthracene can be obtained. When anthracene and tetralin are heated together in a sealed tube in the presence of a palladium catalyst, the reaction resembles a catalytic hydrogenation of anthracene and a 61% yield of 1,2,3,4-tetrahydroanthracene along with small amounts of 9,10-dihydroanthracene, and 1,2,3,4,5,6,7,8-octahydroanthracene are obtained. This type of hydrogenation of anthracene can also be achieved with 2-cyclohexenone. The dehydrogenation of 9,10-dihydroanthracene in the liquid phase results in expulsion of less than the theoretical quantity of hydrogen and formation of some 1,2,3,4-tetrahydroanthracene. 1,2,3,4-Tetrahydroanthracene can be conveniently prepared in good yield by refluxing an ethanol solution of anthracene or 9,10-dihydroanthracene with Raney nickel. © 1944, American Chemical Society. All rights reserved.