Multilayer coextrusion combines multiple polymers in a layered structure to produce properties that are not found in a single polymer. Depending on the product, the number of layers can vary from two layers to hundreds of layers. For several of our reinforcement, electronic, shielding, and barrier applications, one of the layers must also include large volumes of various fillers. As the number of layers is increased the layer thickness will decrease to below 5 microns. As a result, the fillers must be on the nanometer size scale. For many nanoscale fillers, high concentrations (> 30 vol %) can lead to aggregation and poor dispersion in the polymer. In addition, at high loadings, the nanoparticles will significantly increase the viscosity resulting in processing difficulties. As a result, we have developed several strategies for maximizing nanoparticle loading while decreasing the impact on the viscosity to aid in the production of filled multilayer structures by coextrusion.