The potential of mid-infrared spectroscopy (MIR), using an attenuated total reflectance (ATR) cell, was evaluated for the authentication of 25 Gruyere PDO and L'Etivaz PDO cheeses produced at different altitudes in Switzerland. In order to test the ability of MIR to authenticate the investigated cheeses, chemometric tools, such as principal component analysis (PCA) and factorial discriminant analysis (FDA), were applied to the three spectral regions of the MIR (e.g. 3000-2800 cm(-1), 1700-1500 cm(-1), and 1500-900 cm(-1)). By applying the FDA to the first 10 principal components (PCs) of the PCA applied to each spectral regions, the best rate of correct classification was obtained in the 3000-2800 cm(-1) and 1500-900 cm(-1) spectral regions, since 90.5% and 90.9% were achieved, respectively. It can be concluded that these two spectral regions could be considered as valuable tools for the determination of the geographical origin of the investigated cheeses. (c) 2007 Elsevier Ltd. All rights reserved.