A multilayer structure composed of Ni, Cr and Si thin films was sputter deposited onto smooth Si(lll) substrates with individual layer thicknesses between 20 and 60 nm. Interfacial reactions and diffusion processes were activated in a differential scanning calorimeter between room temperature and two different temperatures of 380 and 550 degrees C at a rate of 40 degrees C min(-1). Auger electron spectroscopy (AES) depth profiles of the heat-treated samples showed a strong reaction between the Ni and Si layers and different stages of the formation of two nickel silicides, Ni2Si and NiSi, which were identified by transmission electron microscopy (TEM) investigations and by differential scanning calorimetry (DSC) measurements. Their formation strongly depends on the reaction time and temperature and on the relative amounts of Si and Ni which are available for the reaction. A much less pronounced reaction between Cr and Si can be recognized from AES depth profiles and TEM investigations. The combination of DSC, AES and TEM investigations allows a detailed identification of reaction products in the thermally treated multilayer structures.