The phonon frequencies, E(S), measured as the energy differences between zerophonon hole peak and pseudophonon side hole peak in photochemical hole bun-ling (PHB) spectra, were studied for tetraphenylporphin (TPP) in epoxy resin films under various conditions of sample preparation and annealing. The values of phonon frequency, E(S), reflecting low energy excitation modes of the matrix epoxy resins were about 13 to 16 cm-1. They decreased when the epoxy resin was cured at relatively low temperatures and vice versa. At the same cure temperatures the sample quenched to liquid nitrogen showed a lower value than that of the annealed sample. These results are in agreement with the results of qualitative free volume measurements. The thermal stability of holes burned at 20 K was also tested, and the results were compared with the extent of cure and glass transition temperature of the resins.