Abstract: Based on an assumption that the effective pressure in hot pressing related to the applied pressure varies with the relative density of the compact in a power law form. a three-dimensional viscoelastic model that depicts the viscoelastic detormation behaviour of powder compacts in hot pressing has been developed. It has been shown by the experimental data that the proposed model in which the parameters are determined by means of nonlinear regression analysis can be used to describe the density-time relationship for the hot pressing of pure magnesium oxide and atomized iron powders and to estimate the end-point relative density of the compact.