The synthesis, characterization, mesomorphism and ferroelectric behaviour of ten new chiral dimeric compounds are reported. These compounds are non-symmetric dimers consisting of two mesogenic units joined by two different flexible spacers derived fromS(−)-lactic acid. The mesogenic units contain ester and thioester groups. The effects of the length of the flexible spacer and the structure of the mesogenic units on the mesomorphism of the compounds are investigated. These compounds are ferroelectric and the spontaneous polarizations of some were measured, giving values ofc.10nC cm−2.