The mesomorphic properties of some binary mixtures consisting of 4-alkoxyphenyl 4-(2-R- or 4-R-3-alkoxybenzoyloxy)benzoates (R=H, CH3, Br, or CN) and 4-cyano-4'octyloxybiphenyl or 4-pentyloxyphenyl 4-[(4-octyloxy)benzoyloxy]benzoate were examined. In the binary phase diagrams an enhanced and/or induced smectic A phases were observed, even if both components have terminal polar group. The mesomorphic properties are discussed in terms of both electrostatic nature of substituents and molecular shapes of both components.