Adsorption at surfaces has been a topic of considerable interest since Gibbs introduced his famous adsorption equation in 1875. However, only in the past few years, has adsorption become quantitatively understood (at least in the vicinity of a critical point). Adsorption is far more complex than perhaps one might envision. At the liquid–vapour interface of a binary liquid mixture one can find: (i) strong adsorption (where one component completely saturates the surface); (ii) competitive adsorption (where the two species compete for surface sites); and (iii) dipole surface orientational order (due to dipole-image dipole interactions). In this paper we discuss these various modes of adsorption.