In thermotherapy, the efficiency of a peloid depends in particular on its thermal quality and an appropriate and detailed chemical and physical characterization is necessary to understand the thermal behaviour of these products. The most influential physical properties are the specific heat capacity, the thermal conductivity and the density. This work focuses on the study of the evolution of those properties of Dax peloid mixed with thermal and mineral water as a function of the mud concentration. The experimental specific heat capacity data were measured using a Calvet calorimeter, SETARAM BT 2.15, which permits studying with high precision all kind of substances and materials (oils, polymers, hydrates, powders) and simulate almost any process condition (reactions. crystallisation, freezing, etc.) and in the temperature range from 298.15 to 314.15 K. The pycnometer method and an Anton-Paar DMA-4500 vibrating-tube densimeter were used to measure density values while the thermal conductivity was determined by the Model KD2 Pro, Decagon Devices Inc. The experimental data show the expected behaviour: the specific heat capacity increases with temperature and decreases with concentration whereas density decreases with temperature and increases with concentration. Besides the thermal conductivity increases with both temperature and concentration. The results of this study will be used to determine the best proportion between peloid and mineral water for an individual mud bath. (C) 2012 Elsevier B.V. All rights reserved.