This study was conducted to clarify the clinical and neurophysiologic characteristics of patients with Morvan syndrome, and to compare and contrast this syndrome with other forms of autoimmune encephalitis. A retrospective chart review of the clinical features and neurophysiologic studies of two cases of Morvan syndrome seen at the Mayo Clinic was performed. Neurophysiologic studies included polysomnography, comprehensive autonomic testing, MRI, positron emission tomography, EEG, and single-photon emission computed tomography. In two cases of Morvan syndrome, the clinical features, electrophysiologic findings, and immunologic studies (high levels of voltage-gated potassium channel antibodies) were consistent with previously reported findings. Several novel observations were made. Autonomic testing demonstrated peripheral autonomic neuropathy in addition to autonomic hyperactivity. Polysomnography showed complete absence of sleep. Neuroimaging study findings were largely normal. Morvan syndrome is an autoimmune disorder affecting both the peripheral and central nervous system. Neurophysiologic studies demonstrate hyperexcitability of peripheral nerves, autonomic dysfunction, and severe insomnia. The absence of abnormalities on imaging studies suggests that central nervous system symptoms are related to functional rather than structural disruption of neural networks.