The last three decades has seen the development of neutron scattering techniques as probes for the nanoscale structure of polymer filled and nanocomposite polymer systems. The objectives of these studies includes understanding filler associations, bound polymer conformation and interactions of bound and matrix polymer and the relationship between these and mechanical properties with the goal of determining the mechanism of reinforcement. This information is central to the development of improved composites. Although this goal has not yet been attained, fundamental and unique information has resulted. In this presentation, I review the new information that we have obtained from the elastic neutron scattering probes of nanoscale composite and filler structure. I also discuss the prospects of these techniques in achieving our long-term goals.