Liquid crystalline naphthalene derivatives of the formula ##STR1## wherein ring A is 1,4-phenylene, trans-1,4-cyclohexylene or 1,4-cyclohex-1-enylene and ring system BC is 2,6-naphthylene, 3,4-dihydro-2,6-naphthylene or 1,2,3,4-tetrahydro-2,6-naphthylene, with the proviso that A is not 1,4-phenylene when BC is 2,6-naphthylene; and R.sub.1 and R.sub.2, which are identical or different, are each alkyl of up to 8 C atoms or, when the rings to which they are bonded are aromatic, also can be alkoxy, alkanoyloxy or alkoxycarbonyloxy having up to 8 C atoms in each case; or one of R.sub.1 and R.sub.2 also can be CN, halogen, CF.sub.3 or NO.sub.2 are valuable components for liquid crystalline dielectrics.