[en] Full text: Continuous search of new inorganic materials with promising properties to replace existing conventional ones in the industry has been leading to the development of alloys with unique compositions, such as metal matrix composites (MMCs), nanostructured metal(metal oxide)/polymer composites, and high-entropy alloys (HEAs). It is quite complicated to predict the structure and properties of such materials due to the lack of experimental data related to interactions between structural constituents in those under different conditions. This essential prerequisite has been encouraging a blazing fast increase in articles related to these topics, especially HEAs. The main goal of the present study was to receive a set of reliable thermophysical data (density, molar volume) of the liquid phase of the AlCoCrCuFeNi HEA and their sub-system alloys. For experimental investigation, samples were prepared by arc-melting method. The measurements were performed using an electromagnetic levitation facility designed for optical dilatometry. The excess molar volume was calculated based on the experimental density values of the investigated alloys and data of those for pure liquid metals, previously measured by ourselves Furthermore, the integral enthalpy of mixing of the AlCoCrCuFeNi alloy family was calculated based on Miedema’s model. A good agreement between the excess molar volume and the integral enthalpy of mixing was obtained. (author)