A perturbation technique is used to calculate the thermodynamic properties of nitromethane for high pressures. The intermolecular interaction is described by a spherically symmetric, exponential‐6 potential and an angular dependent, multipolar contribution. Isothermal compression and the shock Hugoniot for nitromethane are well characterized by the theory. Molecular dynamics calculations, with the intermolecular forces constructed from interatomic interactions, also describe the experimental observations under consideration. There is a considerable difference in the predicted shock temperatures from the two methods. © 2004 American Institute of Physics