Abstract: The present invention relates to a proccss for preparing cis-(1S)-N-methyl-4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-1-naphtalenami ne and its acid addition salts wherein N-methyl-[4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-naphtalene-1-en]-amine -N-oxide is hydrogenated in an inert solvent in the presence of a catalyst, then the resulting mixture is treated with alcanolic solution of a mineral acid, the resulting cis-racemic acid addition salt is converted to the free base by known methods, resolved and the resulting cis-(+)-base of formula (II) is converted to an acid addition salt. N-methyl-[4-(3,4-dichlorophenyl)-1,2,3,4-tetrahydro-naphtalene-1-en]amine- N-oxide is also disclosed.