Ferroelectric smectic liquid crystal mixtures are provided consisting of two constituents; a smectic host and another containing a chiral compound in which rotation of the chiral centre relative to the molecular core is sterically hindered, so that the chiral compound induces a high Ps in the mixture. A preferred class of chiral compounds is those derived from naturally occurring compounds with chiral groups, especially alpha-hydroxycarboxylic acids, amino acids and terpenoids, e.g. with chiral groups (I), (II), (III). The chiral group is incorporated into a compound containing a mesogenic combination of groups, e.g. with chains of cyclic groups and some mesogenic combinations are described.