We report on 2 patients who presented stiffness and spasms similar to those of stiff-man syndrome (SMS) that were limited to one leg for up to 11 years. Patients had serum glutamic acid decarboxylase (GAD) autoantibodies in high titer, clinical evidence of organ-specific autoimmunity, and electromyographic pattern of continuous motor unit activity with abnormally enhanced exteroceptive reflexes. The clinical and immunological profile suggests that this disorder may be a focal form of SMS.