The smectic properties of four series of esters — the methyl to n-decyl esters of the 4'-n-hexyloxy, 4'-n-heptyloxy-, 4'-n-octyloxy- and 4'-n-nonyloxy-biphenyl-4-carboxylic acids — are discussed. The effects on the smectic phases of increasing the alkyl chain lengths are quite striking, particularly in the last three of these series, where SC properties are introduced for the midde members. The SC-SA transition temperatures in each series lie on two parabolae with the result that the earlier homologues exhibit A, B, E sequences and the higher homologues form only SA phases. Thus, the tendency of these series to exhibit SC phases is a function of alkyl chain length and is not determined simply by the more rigid central part of the molecule containing the permanent dipole moments. Evidence for the SC properties of these esters is given in detail. Other cases in which increasing the alkyl chain length leads to marked changes in smectic polymorphic behaviour, including the sudden injection of different smectic polymorphic phases into particular sequences of smectic phases, are reviewed