The standard (p degrees = 0.1 MPa) molar enthalpies of formation for crystalline 2-cyanoquinoline, 2-CN-C9H6N, and 3-cyanoquinoline, 3-CN-C9H6N, were derived from the standard molar enthalpies of combustion, in oxygen, at the temperature T = 298.15 K, measured by static bomb-combustion calorimetry; the Knudsen mass-loss effusion technique was used to measure the vapour pressures of the crystals as functions of temperature, and the standard molar enthalpies of sublimation, at T = 298.15 K, were derived by the Clausius-Clapeyron equation. Direct measurements of the standard molar enthalpies of sublimation, using microcalorimetry, for 2-cyanoquinoline and 3-cyanoquinoline confirmed the values from the Knudsen technique. [GRAPHICS] (c) 1995 Academic Press Limited