THIOPENTAL, A BARBITURATE anesthetic, which at high doses suppresses cortical electroencephalogram activity, was evaluated as a neuroprotective agent in a dog model of reversible, hindbrain ischemia. Fourteen dogs were exposed to 20 minutes of isolated brain stem ischemia after pretreatment with 35 mg per kg of thiopental or placebo. Brain stem auditory evoked potentials (BAEPs) and regional cerebral blood flow were measured before and during the ischemia and for 5 hours after reperfusion. During the ischemic period, both control and thiopental-treated animals experienced dramatic declines in the BAEPs to less than 10% of baseline. On reperfusion for 30 minutes, the BAEPs increased in both groups to near 40% of baseline. In the thiopental-treated animals, the BAEPs continued to recover variably to a mean of 70% of baseline by 5 hours of reperfusion. In contrast, untreated animals showed a decline in BAEPs after 30 minutes of reperfusion. The improved recovery of BAEPs in the thiopental-treated animals suggests that thiopental may be of some value as a cerebroprotective agent, although the mechanism remains unclear. The variability in recovery in this group implies that other factors play a significant role in mediating functional recovery from ischemic brain stem damage.