Excess molar enthalpies, H-m(E), of binary liquid mixtures containing ethylene glycol (EG),propylene glycol (PPG),di(ethylene glycol) (DEG), tri(ethylene glycol) (TEG), tetra(ethylene glycol) (TETG), or some PEGs, as PEG200, PEG300, PEG400, PEG600, +3-phenylpropyl alcohol (PPAL) have been measured over the entire range of composition at 308.15 K and at atmospheric pressure, using a flow microcalorimeter. The H-m(E)'s vary from a value of -200 J mol(-1) (mixture containing PEG600 or DEG) up to a maximum of 350 J mol(-1) (mixture containing propylene glycol), decreasing as the chain length of PEGs increases. Curves are not symmetric and, in the case of mixtures containing PEGs, an intersection among the curves has been observed. Results were fitted to the Redlich-Kister polynomial to estimate the adjustable parameters and the standard deviations between experimental and calculated values. The results are discussed in term of both intermolecular H-bonding and variation in molecular conformation of PEGs. (C) 2004 Elsevier B.V. All rights reserved.