Electron energy band structure in polymers, particularly polyethylene, and electron injection, transport and trapping are briefly reviewed. The interface model of polymer nanocomposites is then described, and the Tanaka et al. and Lewis formulations of the model outlined in the context of a mechanistic understanding. Detailed discussion of several recent papers, presenting DC conductivity and space charge data for seven different polymer/nanoparticle combinations, follows. The main findings for each combination are summarized. It is concluded that the DC conductivity and space charge accumulation data discussed do not specifically endorse the interface model of nanodielectrics. Rather the data presented can be interpreted satisfactorily, though not in detail, using the established models of charge injection, transport and trapping in polymers, and percolation theory. Finally, broad tentative guidelines for tailoring the charge transport properties of polymer nanocomposites are presented. © 2010 Springer-Verlag US.