The llama (Lama glama) is adapted to live in the low oxygen milieu of the Andean altiplano. The ability of the llama fetus to grow and develop successfully in this adverse environment suggest very efficient adaptive mechanisms to withstand hypoxia. The llama fetus responds to acute hypoxaemia with a reduced increase of brain blood flow and a substantial reduction of the brain O2 consumption (Llanos et al, 2003). These observations are consistent with a marked cerebral hypometabolism in the hypoxaemic fetal llama as a strategy to preserve the CNS integrity. We hypothesise that the llama fetus brain responds to prolonged hypoxaemia with some degree of hypometabolism, decreasing the Electrocorticographic activity (ECoG)and Brain Temperature (BT). Therefore, we studied the brain ECoG , the BT and carotid blow flow (CBF) in llama fetuses subjected to a prolonged hypoxaemic period of 24h. Eight llama fetuses (5 normoxaemic (NG; maternal FiO₂ 0.21), 3 hypoxaemic (HG; maternal FiO₂ 0.1)), between 0.6—0.8 gestation, were chronically instrumented under maternal and fetal general anaesthesia (sodium thiopentone 10—12 mg kg-1 i.v.; 1% inhalatory halotane). Approval was obtained from the local Ethics Committee. In the fetuses, we placed a transonic flowmeter in the common carotid artery, bipolar electrodes in the parietal duramater, and a thermistor in the brain parietal cortex and central arterial and venous catheters. Arterial blood samples were obtained every hour; CBF, ECoG and BT were registered continuously during 24h in hypoxaemic and normoxaemic fetuses. The PO2 in the HG decreased when compared with the NG (13.2±0.8 vs. 18.6±0.8 mmHg, p< 0.05) with no changes in pH or PCO2. The CBF increased after 8h of the experimental protocol in the HG (29±5 vs. 14±1.0 ml min-1 Kg-1, p< 0.05), while BT tended to decrease progressively in this group The fetal ECoG showed a tendency to increase the percent of time in high voltage-low frequency state during hypoxaemia, state which has a lower brain O2 consumption. The increase in carotid blood flow in the hypoxaemic fetuses, could be the result of a rise in the brain-stem blood flow, whilst the brain cortex hypometabolism could be suspected by the tendency to drop in brain temperature and to increase in the percent of time in high voltage-low frequency state, even when differences did not reach significance. These findings suggest that the brain of the llama fetus adapts very effectively to a prolonged episode of hypoxaemia.