The mesomorphic properties of 4-(4 alkoxybenzylideneamino)phenyl 2- and 3-X-benzoates, whereX= Me or Cl, were examined. While the nematic-isotropic transition temperatures of the 2-Me and 2-Cl derivatives are nearly identical, the 3-Cl derivatives give higher transition temperatures than the 3-Me derivatives, the difference being 20°C or more. The nematic phase given by the lower homologous members of the 2-Me derivative is thermally more stable than that of the 3-Me derivative but this relation is reversed for the higher members. In contrast to the purely nematogenic parent compounds, the 3-halogeno derivatives of the higher homologous members exhibit a smectic A phase.