We report measurements on the temperature variation of the electroclinic coefficient (e) of three members of a homologous series and a commercial ferroelectric mixture. The pure compounds haveP/θ ratios which are an order of magnitude larger than that of the commercial mixture. This is reflected in the temperature variations of the electroclinic coefficient. Plots ofe−1versus temperature indicate that in all the four cases the Landau theory gives a good description of the critical divergence ofeas the S*C–SAtransition point is approached. We have made a detailed analysis of the data on one compound using the Garoff-Meyer model to confirm that the critical behaviour for the soft mode is indeed well described by the Landau theory.