Cerebral blood flow was measured in normal waking (alert relaxed mental imagery) and hypnotic states. Mean flow velocity (Vm) in the middle cerebral artery (MCA) was significantly increased in hypnosis (Condition 11) from Condition I (5 minutes before hypnotic induction). Vm decreased in Condition III (hypnotic imagination). After hypnosis, Vm values returned to baseline. Pulsatility index values and resistive index values showed significant variations during sonographic monitoring between Conditions I and IV (5 minutes after the completion of hypnosis). Both values were significantly higher in Condition I than IV. These findings show that hypnotic status can modulate cerebral blood flow.