It has ben postulated recently that Sodium Pentothal has the cerebral protective effect during hypoxia by its efficacy of decreased cerebral oxygen consumption(CMRO2) by as much as 40 to 50 per cent. It could, potentially, improve regional or total cerebral perfusion in cases of acutely elevated intracranial pressure due to cerebrovasodilation and augmentation of cerebral blood volume, although Sodium Pentothal reduces cerebral blood flow in normal persons. Our study was designed to evaluate the effects of Sodium Pentothal on respiration, which were frequently depressed with 2.5% of Sodium Pentothal as a bolus dose. 0.2% of Sodium Pentothal was administered by continuous intravenous dripping to seven aneurosurgical patients showing uncontrollable seizure and increased intracranial pressure. PH, PaCO2, PaO2, respiratory rate and minute ventilatory values before and after Sodium Pentothal infusion were evaluated. It was observed that the values of PaO2 were improved with minimal changes in pH, PaCO2, respiratory rate and minute ventilatory values.