We report a case of Stiff-Man syndrome according to Gordon, Januszko and Kaufman's criteria. Onset at age 76, association with insomnia and a rapid course leading to death within 2 years were the characteristic features. CSF data, electromyographic and immunological findings suggest abnormalities of catecholaminergic and GABA ergic systems, with release of segmental or suprasegmental inhibitory influence. The presence of antibodies against glutamic acid decarboxylase, considered a useful marker of this syndrome, raises the possibility of an autoimmune pathogenesis.