Intracerebral administration of adrenocorticotropic hormone (ACTH) elicits in experimental animals a yawning stretching behavior which is believed to reflect an arousal response mediated through the septohippocampal cholinergic neurons. A surge in plasma ACTH levels at night and just prior to awakening from sleep is also associated in humans with yawning and stretching behavior. Recurrent episodes of uncontrollable yawning and body stretching, identical to those observed upon awakening from physiological sleep, occur in a subset of patients with multiple sclerosis (MS) during transcranial therapeutic application of AC pulsed electromagnetic fields of picotesla flux density. This behavioral response has been observed exclusively in young female patients who are fully ambulatory with a relapsing remitting course of the disease who also demonstrate a distinctly favorable therapeutic response to magnetic stimulation. ACTH is employed for the treatment of MS due to its immunomodulatory effects and a surge in its release in response to AC pulsed magnetic stimulation could explain some of the mechanism by which these fields improve symptoms of the disease.