The standard (p° = 0.1 MPa) molar enthalpy of formation for gaseous 2-phenylbenzimidazole (2-PhBIM) and 2-benzylbenzimidazole (2-BzBIM) were derived from the standard molar enthalpies of combustion, at T = 298.15 K, measured by static bomb calorimetry, and the standard molar enthalpy of sublimation, at T = 298.15 K, measured by Calvet microcalorimetry in the case of 2-phenylbenzimidazole or derived from the variation of the vapour pressures, determined by the Knudsen effusion technique, with temperatures between (393 and 412) K for 2-benzylbenzimidazole. Heat capacities, in the temperature ranges from (268.15 to 322.10) K for 2-phenylbenzimidazole and (270.15 to 316.02) K for 2-benzylbenzimidazole, were also measured with a differential scanning calorimeter. ΔcHm°(cr)/kJ·mol-1ΔcrgHm°(T=298.15K)/ kJ·mol-12-Phenylbenzimidazole (2-PhBIM)-6679.8 ± 0.9123.0 ± 1.72-Benzylbenzimidazole (2-BzBIM)-7327.1 ± 4.0136.2 ± 0.5 © 2005 Elsevier Ltd. All rights reserved.