We tested the effect of moderate food or water deprivation and a combination of the two on sensitivity to hyperoxia-induced seizures in rats. Seventy rats with chronic cortical electrodes were exposed to seven experimental protocols: starvation, dehydration or a combination of both for 24 or 36 h, prior to exposure to 0.5 Mp a O 2 . Blood glucose and hematocrit were measured before and after exposure to hyperbaric oxygen (HBO). Starvation and dehydration significantly prolonged the latent period to the onset of hyperoxia-induced seizures (P<0.05 in the Tukey test), in a dose-related manner. Our results suggest that deprivation of food or water, prior to exposure to HBO, may postpone the development of hyperoxia-induced seizures.