The application of the technique of atom probe tomography to the atomic scale characterization of interfaces and surface films is described. The three-dimensional atom probe determines the coordinates and elemental identities of the atoms in a small volume of a sample with near-atomic precision. The types of analyses that may be performed on interfaces are demonstrated by examples taken from a variety of materials, including neutron-irradiated pressure-vessel steel welds, superalloys, surface films and model alloys. Published in