In this article, we report on the influence of reactive compatibilization on the morphological and theological properties of blends of polyamide 6 (PA 6) and a styrene-acrylonitrile copolymer (SAN). PA 6/SAN blends with two different composition ratios (70/30 and 30/70) and varying concentration of a styrene acrylonitrile maleic anhydride terpolymer (SANMA) were prepared. During melt mixing, the amino end groups of PA 6 react with the maleic anhydride groups of SANMA. The objective of this work is to study the elastic and viscous properties of the blends in shear and elongation as a function of compatibilizer concentration. The composition ratio of the blends (PA 6 or SAN matrix) has a strong influence on the morphology and rheology of the blends, in particular for large SANMA concentrations. We explain this phenomenon by the asymmetric properties of the reactively compatibilized interface which originates from the comblike architecture of the in situ generated interfacial agent. In linear viscoelastic shear oscillations, the reactively compatibilized PA 6/SAN blends with a PA 6 matrix depict for large SANMA concentrations the power laws G' proportional to G '' proportional to omega(n) with n approximate to 0.58 whereas the blends with a SAN matrix display a solidlike low frequency behavior. In melt elongation, the extensional viscosity of the PA 6/SAN blends exceed its linear viscoelastic prediction for large SANMA concentrations. Furthermore, our AFM investigations of elongated and subsequently quenched samples reveal that the stretch ratio of spherical SAN domains in the PA 6 matrix increases with SANMA concentration. In recovery, these stretched SAN domains recover more slowly to an isotropic shape when the SANMA concentration was increased.