In this work, our objective is to contribute to the knowledge of the mixtures (alcohol + polyalkyl ether glycol) used in absorption refrigeration systems and heat pumps. The determination of different thermophysical properties is essential to understand the interactions among different molecules in liquid mixtures. Therefore, experimental data of speed of sound and density together with calculated values of isentropic compressibility for the refrigerant-absorbent system (methanol + polyethylene glycol dimethyl ether 250) (or Pegdme 250) have been gathered here over the whole range of composition at temperatures from T = 293.15 to 333.15 K and atmospheric pressure. The two previous experimental properties were measured with a digital vibrating tube analyser Anton Paar DSA-48. Also, the excess molar volumes and the increments of the speed of sound and the isentropic compressibility have been determined for each composition and they were fitted to a variable-degree polynomial equation. (C) 2003 Elsevier Science Ltd. All rights reserved.