Stiff-man syndrome (Moersch-Woltman syndrome) is a rare disorder of motor function characterized by involuntary stiffness of axial muscles and superimposed painful muscle spasms, which are often induced by startle or emotional stimuli. The standard treatment has been benzodiazepines. An association has been reported between stiff-man syndrome and epilepsy, insulin-dependent diabetes, and a variety of organ-specific autoimmune disorders. Antibodies directed against glutamic acid decarboxylase and against pancreatic islet cells have been detected in the serum and cerebrospinal of patients with stiff-man syndrome. These findings suggest that stiff-man syndrome may be an autoimmune disease. Preliminary reports indicate that patients with stiff-man syndrome have a favorable response to plasma exchange and corticosteroid therapy.