Both peripheral ends of some straight-shaped mesogenic compounds, possessing a biphenyl or azobenzene as a central rigid core, have been systematically modified, and the effect on the liquid-crystalline properties investigated. A fluorinated moiety introduced into the peripheral alkyl chains stabilized the smectic phase, whereas that into the terminally positioned phenyl rings resulted in the appearance of the nematic phase, Introduction of phenyl rings into the middle of the flexible chains produced a well-defined smectic layered structure. Further introduction of another phenyl ring at each terminal end was found to show a significant effect on the determination of the clinicity.