The present paper seeks to establish a theoretical framework to account for the spontaneous molecular ordering at free surfaces of molecular aggregates. It is shown that within a multipole representation of the molecular interactions, ordering is the effect of the interplay of two fundamental causes: the translational symmetry breaking of the bulk phase at the interface and the interactions of multipoles of different parity. Quantitative analysis of the order parameter demonstrates the building up of ordering at different length scales with range depending on the strength of the interactions. (C) 2017 Elsevier B.V. All rights reserved.