We investigated blood flow to the facial nerve, cerebral cortex, brain stem, and dura mater in 16 white rabbits using a nonradioactive microsphere technique at various levels of arterial carbon dioxide tension. The blood flow to the facial nerve in the 32 temporal bones was 59.1 +/- 32.9 microliters/g/min. Unlike cerebral blood flow, blood flow to the facial nerve and dura mater did not show any marked increase upon carbon dioxide inhalation.