Abstract Auger electron spectroscopy (AES) is usually used in conjunction with inert gas ion sputtering to obtain composition-depth profiles through surface layers. In certain cases the mechanical lapping of a taper through this region prior to analysis by AES is advantageous in terms of the depth resolution achieved. The regimes of preference of each technique are delineated by considering individually each of the terms contributing to interface degradation for the various types of layered structures encountered in practice, e.g. evaporated films and oxide layers. Illustrations of the effects of relevant parameters are given by measurements for a sharp deep interface between silver and iron.