The enthalpy of combustion of crystalline 4-nitrophenyl azide has been determined by static oxygen bomb calorimetry at 298.15 K as - (3241.4 +/- 4.2) kJ mol(-1). The corresponding enthalpies of formation using an estimated enthalpy of sublimation are Delta(f)H(m)(0) = (308.7 +/- 4.3)(c) and (389.7 +/- 5.2)(g) kJ mol(-1). The predictive capacity of the Laidler and Pedley bond energy schemes as applied to organic azides is explored.