The standard (pdegrees = 0.1 MPa) molar enthalpies of formation of liquid pyrazinecarbonitrile and of crystalline pyrazinecarboxylic acid and pyrazinamide were measured, at T = 298.15 K, by static bomb calorimetry and the standard molar enthalpies of vaporization or of sublimation, at T = 298.15 K, were obtained using Calvet microcalorimetry. These values were used to derive the respective standard molar enthalpies of formation in gaseous phase. (C) 2004 Elsevier Ltd. All rights reserved.