1,1,3,4,4,6-Hexamethyl-1,2,3,4-tetrahydronaphthalene (HMT), which is an intermediate for the production of acetyl HMT valuable in the art of perfumery because of its musk-like odor properties, is produced with industrial advantages by reacting p-cymene with 2,3-dimethylbutene using a catalytic amount of an anhydrous aluminum halide in the presence of at least one member selected from secondary alkyl halides, tertiary alkyl halides, propargyl halides and allyl halides; and 7-acetyl HMT is obtained by acetylation of the above-obtained HMT.