Parts are produced from steel powder in a two step process : the powder is first compressed in a hard matrix and then sintered under a reducing atmosphere. During the second step, the part may be submitted to non-isotropic strains. Based on different experimental set-ups, the effect of the applied strain on the part deformation anisotropy has been assessed. This anisotropy increases with the density of the raw compressed material. The actual viscosity of the material has been derived from the measured strains with the help of a simple analytical model. The possible application of these results, to predict the shape alterations of industrial parts during sintering, is then discussed.