This paper reports the values of the standard (p = 0.1 MPa) molar enthalpy of formation in the gas phase, at T = 298.15 K, for 3-hydroxypropanenitrile derived from the respective enthalpy of combustion in oxygen, measured by static bomb combustion calorimetry and the standard molar enthalpy of vaporization, at T= 298.15 K, determined using the transference (transpiration) method in a saturated N-2 stream, the value of the gas-phase enthalpy of formation being Delta H-f(m)degrees (g) = -(91.2 +/- 1.4) kJ center dot mol(-1). Furthermore, we have performed high-level ab initio molecular orbital calculations at the G3 level. Four different conformations corresponding to local minima of the potential energy surface have been found for 3-hydroxypropanenitrile. The optimised molecular and electronic structure of the most stable conformer of 3-hydroxypropanenitrile shows a gauche arrangement with a weak intramolecular hydrogen bond from OH hydrogen to the pi-bond charge cloud of the nitrile group. The calculated values for the enthalpy of formation of the most stable conformer using atomization and isodesmic bond separation reactions, -94.7 and -95.0 kJ center dot mol(-1), respectively, are in very good agreement with the experimental value. (c) 2007 Elsevier Ltd. All rights reserved.