There is significant interest in the application of siliconon-insulator (SOI) technologies in environments requiring substantial radiation hardness. In such environments, trapping of charge carriers in the buried oxide is of some concern. We have begun to explore trapping centers in SIMOX buried oxides using a combination of electron paramagnetic resonance (EPR) and vacuum ultraviolet (hc/λ- = 10.2 ev) and ultraviolet (hc/λ = 5 ev) irradiation sequences. In this abstract, we present experimental evidence which strongly indicates that E' centers or E' like centers play an important role in hole trapping in SIMOX oxides. The E' center is a silicon back-bonded to three oxygen atoms; in thermally grown SiO2 films on silicon it is the dominant deep hole trap and is almost certainly a hole trapped in an oxygen vacancy.