This work deals with the relationship between microstructure, melt viscosity, and copolymer concentration of PAmXD,6/PP-g-MA blends [poly(m-xylylene adipamide)/maleic anhydride functionalized polypropylene]. The blends were processed in a Brabender plastograph at a temperature of 265 +/- 5 degrees C and at 45 rpm. The characterization of the microstructure was carried out through SEM analysis after microtome leveling and chemical etching. The melt viscosity of the components and of the blends was measured by the Brabender torque. It was found that the copolymers concentration controls the dimension of the dispersed phase. The composition of the blend (dispersed phase weight percent) has a more limited influence. Variations of the components viscosity ratio during the mixing time have little, if any influence on the dimension of the dispersed phase. A Linear relation between the Brabender torque and the specific interfacial area was found. The determination of the copolymer weight fraction leads to the establishment of a close relation between the copolymer concentration and the specific interfacial area. For blends containing from 0 to 7.5 wt % of copolymer, this relation is Linear and consequently the concentration of copolymer at the interface is constant at about one copolymer macromolecule per 16 nm(2).