Liquid crystalline transition temperatures in 4-(2-and 3-X-benzylideneamino)phenyl 4-alkoxybenzoates, where X = Me or C1, were examined. Although the two substituents are geometrically similar, they affect the nematic-isotropic transition temperature differently. The transition temperature of the 2-Me derivative is higher by 10 to 15°C than that of the 2-C1 derivative, whereas the reverse is true for the 3-X derivatives, the difference being 14 to 21°C. The 3-halogeno derivatives of the higher homologous members exhibit a smectic A phase which is not observed for the parent compounds.