Enthalpies of vaporization of 2- and 3-methoxythiophenes (48.32 +/- 0.30 and 48.54 +/- 0.22 kJ.mol (1), respectively) have been measured by the transpiration method using nitrogen as the carrying and protecting stream. Combustion experiments leading to enthalpies of formation in the liquid phase, Delta H-f(0) m(l), for both isomers failed due to rapid darkening of freshly distilled samples even under a protecting atmosphere. However, combination of experimental vaporization enthalpies with values of the gaseous enthalpies of formation, Delta H-f(m)0(g), obtained by quantum-chemical calculations from our previous work Notario et al. (2012) [24] permits establishing estimated Delta H-f(m)0(l) values of -(68.3 +/- 4.2) and -(80.1 +/- 4.2) kJ.mol (1), for 2- and 3-methoxythiophene, respectively. (C) 2013 Elsevier Ltd. All rights reserved.