We have studied the effect of the amount phi(C) of a reactive compatibilizer on the rheological properties of a polyethlene/polyamide blend, under steady shear and transient extensional flows. Here, we propose to describe th viscosity eta(gamma) and the first normal stress coefficient psi(1)(gamma) using a Carreau-type power-law model, which is a three-parameter model. A single model is sufficient to express the behavior of psi(1)(gamma). On the other hand, the complete eta(gamma) curve is described by the superposition of two Carreau models, in relation to the presence of two relaxation mechanism. Moreover, the extentional viscosity eta(E)(epsilon), estimated using the end pressure drop observed in capillary flow experiments, is expressed by a two-parameter power-law model.