One of the prime tasks of a mining engineer is to calculate the mine cooling load necessary for mine air conditioning system, which must provide suitable working conditions for the work force primarily at the working faces. Additionally the determination of thermal parameters of rocks plays an important role in the activities of geothermal energy production, energy storage and radioactive waste disposal. These activities require the determination of thermal conductivity coefficient of rocks especially around underground openings. This paper deals with the results of the variation of thermal conductivity of rocks with uniaxial and triaxial stress at the laboratory scale. In this way, it is possible to see the difference between thermal conductivity coefficient values under uniaxial and triaxial stress and to draw the conclusions necessary to be taken into consideration for heat flow calculations. To this end, rock specimens have been tested via a new device developed by authors. The results obtained from the tests performed with this device, as given in the related plots, show that the thermal conductivity coefficients determined are suitable for use to support design analyses. (C) 2004 Elsevier Ltd. All rights reserved.