X-ray interference (XRI) is a powerful technique widely used in the structural characterization of epitaxial III-V semiconductor layers. It is particularly useful in determining the thickness and composition of a layer C in a structure B/C/B, where layer C is much thinner than the B (cladding) layers. Using this technique, layers of nanometer thickness can be resolved easily. XRI has not been extensively used to study II-VI semiconductors. In this paper we demonstrate the use of XRI in investigating the structural properties of two different II-VI semiconductor alloy systems. Firstly, we show how XRI can accurately determine the thickness and composition of thin ZnCdSe layers in ZnSe/ZnCdSe/ZnSe structures, and also that the onset of relaxation in the structure can be seen. Secondly, we show how XRI was used in the initial stages of our investigation of MgS, where initially little was known about the basic materials parameters. (C) 2002 Elsevier Science B.V. All rights reserved.