Primary brain ischemia following subarachnoid hemorrhage is a major cause of morbidity and mortality. This study aims to determine whether changes in cerebral tissue oxygenation are related to cerebral blood flow changes in the acute phase following experimental subarachnoid hemorrhage. The endovascular puncture model was used to study subarachnoid hemorrhage in male Wistar rats with a tissue oxygenation probe and a laser Doppler probe placed contralateral to the side of hemorrhage. Following the subarachnoid hemorrhage intracranial pressure rose to 53.0 +/- 9.8 mmHg (mean +/- SEM). This was associated with a fall in cerebral blood flow to 43.9% +/- 7.1% of its baseline value and a fall in tissue oxygenation to 42.8% +/- 7.7% of baseline. The time course of the fall and recovery in tissue oxygenation was closely correlated to that of the cerebral blood flow (r = 0.66, p = 0.02). The fall in cerebral blood flow was associated with a 42.1% +/- 6.47% fall in the concentration of moving blood cells and a rise of 181.2% +/- 27.2% in velocity indicating acute microcirculatory vasoconstriction. Interstitial tissue oxygenation changes mirrored changes in cerebral blood flow indicating that a change in oxygen delivery was occurring.