We report on a 28-year-old woman with insulin-resistant diabetes mellitus with a 5-year history of progressive stiffness and painful spasms of the right leg, exaggerated by sudden auditory and tactile stimuli or by emotional stress. There were no signs of truncal rigidity or exaggerated lumbar lordosis. Anti-glutamic acid decarboxylase antibodies were positive in her serum. She improved substantially with clonazepam 4 mg/day. She presented with electrophysiological findings not previously reported in stiff leg syndrome, which may suggest increased inhibition in the uninvolved upper extremities. © 2001 Movement Disorder Society.