The synthesis and mesogenic properties of some lateral fluoro substituted 4-(trans-4-(n-propyl)cyclohexylethyl)-4’-thiomethylbiphenyls and 4-n-alkyl-4 "-thiomethylterphenyls are described. Birefringence (Delta n) and dielectric anisotropy (Delta epsilon) measurements for these compounds are also given and compared with analogous terminal chloro, cyano and methoxy compounds. It is found that the use of a terminal thiomethyl group produces compounds of intermediate Delta n, Delta epsilon and clearing point than analogous terminal chloro, methoxy and cyano compounds. The terminal thiomethyl group is also more smectogenic than any of the other three terminal endgroups. In most cases, however the melting points of the compounds are too high to be of practical use.