This report presents a study of the thermodynamic properties of 9-fluorenone and 9-fluorenol. The standard enthalpies of formation of 9-fluorenone and 9-fluorenol in the crystalline phase at T = 298.15 K were determined from the energies of combustion in oxygen as -(11.4 +/- 3.8) kJ.mol(-1) and -(66.3 +/- 2.9) kJ.mol(-1), respectively. Vapor pressures of the two compounds were measured at several temperatures using two different experimental methods (Knudsen effusion for crystalline-phase vapor pressures and a static method for crystalline- and liquid-phase vapor pressures), which yielded reliable values of the enthalpies of sublimation, vaporization, and fusion. The sublimation and fusion enthalpies were also determined using calorimetric methods. The enthalpies of sublimation at T = 298.15 K were derived from the static vapor pressure measurements as (95.1 +/- 0.5) kJ.mol(-1) for 9-fluorenone and (108.3 +/- 0.5) kJ.mol(-1) for 9-fluorenol. The results enabled the determination of the standard Gibbs energy of the aerobic reactions of oxidation of fluorene to 9-fluorenol and 9-fluorenone and of the oxidation of 9-fluorenol to 9-fluorenone. Values of the standard enthalpies of formation in the gas phase were also calculated.