The crystal structures of α,ω-bis(4-n-pentylanilinebenzylidene-4′-oxy)butane and α,ω-bis(4-n-pentylanilinebenzylidene-4′-oxy)pentane have been determined by single crystal X-ray analysis. These molecules have even and odd chain length spacers linking two mesogenic groups, respectively, and are members of a family of symmetric liquid crystal dimers which possess a rich smectic phase polymorphism, as well as pronounced odd—even effects in the transitional properties as the parity of the central spacer is varied.