The heat capacity of pentafluorobenzene has been measured over the temperature ranges 12–219°K(crystal), 231–324°K(liquid), and 368–498°K(vapour). The heat of fusion of the crystal and the heat of vaporization of the liquid were also determined. Entropies of crystal, liquid, and ideal gas have been calculated from the thermal data. The entropies at 298·15°K are 275·9 (liquid) and 377·8 (gas, 1 atm.), joule deg.–1 mole–1. Correlation of the thermal measurements on the vapour is discussed.