In this paper, an equation of state is presented, which is able to model the p rho T behaviour of fluids in the critical region, in the low-density limit and at high pressure. The equation is developed in the framework of a local mean held model describing density fluctuations in a fluid. This model is based on an earlier developed model, which was employed to describe the p rho T behaviour in the critical region for several substances. It is extended here to high pressure. For the representation of the critical isotherm, argon is used as reference substance. In addition to the experimental data taken from the literature, some state points at high pressure are estimated by the Monte-Carlo simulation on the basis of ab-initio pair potentials. These data were included in the development of the equation of state in order to assure physically correct behaviour at high pressure. With this equation, the p rho T behaviour of argon, sulfur hexafluoride, methane, ethylene, nitrous oxide and carbon dioxide is modeled.