The standard (p(O) = 0.1 MPa) molar enthalpies of formation Delta H-f(m)0(1, or cr) at T = 298.15 K were determined by means of combustion calorimetry for 2-methylnitrobenzene, 2-ethylnitrobenzene, 2-isopropylnitrobenzene, 2-tert-butylnitrobenzene, 2,6-dimethylnitrobenzene, 2,6-di-isopropyl-nitrobenzene, and 2,4,6-tri-tert-butylnitrobenzene. The molar enthalpies of sublimation (or vaporization) of these compounds were obtained from the temperature dependence of the vapor pressure measured in a flow system. The resulting values of Delta H-f(m)0(g) were obtained at T = 298.15 K and used to derive strain enthalpies of alkylnitrobenzenes. The intramolecular interactions of the substituents were discussed in terms of deviations of Delta H-f(m)0(g) from group additivity rules. These values provide a further improvement on the group-contribution methodology for the estimation of the thermodynamic properties of organic compounds.