A thermodynamically consistent equation of state (EOS) was developed for unreacted liquid nitromethane (NM). The specific heat c(upsilon), the coefficient of thermal pressure (partial derivativeP/partial derivativeT)(upsilon), and the isothermal bulk modulus B-T, were modeled as functions of temperature and volume using existing experimental data. To test our EOS predictions, temperature measurements using time-resolved Raman spectroscopy were obtained from NM subjected to stepwise loading. In contrast to previous EOS developments, calculations using our EOS show good agreement with the measured temperatures. Comparison with previous EOS models shows that simplifying assumptions, such as holding (partial derivativeP/partial derivativeT)(upsilon) or Gamma/upsilon constant, lead to significant inaccuracies in temperature predictions for shocked NM. The assumption that the Gruneisen parameter Gamma is a function of volume only is not consistent with our EOS.