The thermoluminescence, phosphorescence and fluorescence spectra of polyethylene, polystyrene, polytetrafluoroethylene and polyproplyene have been recorded. Comparison of these spectra with those of various model compounds indicates that they are due to carbonyl groups attached to the molecular chains. Further evidence is supplied by spectral measurements on polyethylene samples oxidized by heating in air. It is also shown that any luminescent molecule that readily ionizes without dissociation may be regarded as a potential source of thermoluminescence in polymers. The probable role of molecular oxygen as an electron trap is indicated, increasing the thermoluminescence output at low temperatures and decreasing it at higher temperatures.