The thermal conductivity of compact limestones was measured by means of the transient needle-probe method in the field and in the laboratory as well, A comparison of the two procedures indicates that the laboratory measurements are the most representative ones because of a better control of the influence from the surroundings. The water-saturated limestone samples measured under laboratory conditions have thermal conductivities of 2.52–3.34 W m−1K−1and densities of 2520–2690 kg/m3, which are in agreement with standard values. The thermal conductivities were found to increase with increasing density, and a linear correlation ofKw= 4.18 · 10−3ρ −7.97 (W m−1K−1) was obtained as a first approximation by the least squares method.