Simple hydrogen annealing of the buried oxide (BOX) in the range 450 -700-degrees-C was found to introduce net positive charge with areal densities greater-than-or-equal-to 5 x 10(12) cm-2, while H-2 annealing in the range 700 - 1000-degrees-C was observed to activate a neutral state. Both processes appeared reversible upon appropriate vacuum annealing. The charge was sensed in a novel way - using electron spin resonance - through its band bending effect on probed defects in Si layers close to the BOX. A tentative model based on hydrogen incorporation into oxygen vacancies (Si-Si bonds) may account for the results.