The goal of this study was to investigate whether glucocorticoids (GCs) take part in cognition impairment after exposure to chronic low-power-density microwave (MW) fields. We exposed Wistar rats to a 2.45-GHz pulsed MW field at an average power density of 1 mW/cm(2) for 3 h daily, for up to 30 days. Our results show that MW-exposed rats had significant deficits in spatial learning and memory performance. MW exposure increased levels of plasma corticosterone, and consequently GC receptor (GR) nuclear translocation and apoptosis in the hippocampus. However, co-administration of the GR antagonist RU486 with MW exposure partially reversed the cognitive impairment and neuronal loss. These data indicate that GCs might contribute to the cognition deficit induced by chronic low-power-density MW exposure.