A simple pictorial device, the intermolecular force triangleΔv,is introduced, which is capable of representing the structure and the physical content of the theory of intermolecular forces. The structure of the multipole expansion of the interaction potential energy, the first-order interaction energies arising from the interaction of the permanent moments of the interacting species, and the second-order induction and dispersion energies are discussed. Specific interactions are also considered that illustrate the usefulness of the intermolecular force triangle in predicting the various types of interaction energies that can arise in a given atomic or molecular collision.