Commercially available TiO2 and BaSO4 nanoparticles were incorporated in polyamide 6 (PA 6) via twin screw extrusion. The primary particle size of nanoparticles was 15 nm and 20 nm. The compounds were manufactured via multiple extrusion and dilution processing steps. The dispersion of the nanoparticles in the matrix was investigated by scanning electron microscopy and image analysis, micro-tomography, and transmission electron microscopy. The rheological properties were determined via plateplate-rheometer. It was found that for TiO2 fillers a threefold extrusion process is sufficient to realize a dispersion index of 94.4%. BaSO4 fillers were hardly dispersible, ending up with a maximum dispersion index of 71%. Deagglomeration does not lead to a change in rheological properties but the number of extrusion steps decreases the rheological properties. A good particle-matrix interaction leads to higher moduli and viscosity. The remaining agglomerates seem to act as defects decreasing the energy absorption of the respective compounds. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013