A series of vinyl-substituted liquid crystal dimers, -(4-cyanobiphenyl-4'-yloxy)alkyl 4'-(4-pentenyloxy)-4-biphenylcarboxylates, was prepared. The compounds exhibited nematic and smectic liquid crystalline behavior depending on the chain length of the flexible spacer. The nematic-isotropic and smectic-isotropic transition temperatures and the entropy changes associated with the transitions showed odd-even effects as the number of atoms in the flexible spacer was varied, in which the even members exhibited higher values. The liquid crystalline properties of the compounds were compared with those of related known liquid crystal dimers and trimers.