Electrical polarizations in as-cast and electrically polarized films of stretched and unstretched polyacrylonitrile have been measured with the thermally stimulated discharge technique. Preferential orientation of nitrile side groups in polarized specimens is inferred from birefringence and x-ray diffraction experiments, but the contribution of observed persistent electrical polarization appears to be small. The major contribution is concluded as being due to trapped space charges, some part of which may be associated with residual solvent molecules. Small ordered regions within polyacrylonitrile are expected to play a role in development of each contribution to final persistent electrical polarization.