A 53-year-old Japanese woman presented with myoclonus during the course of Guillain-Barré syndrome. The myoclonus was characterized by relatively regular involuntary movements, starting from proximal muscles of the right lower leg, and moving almost simultaneously towards the left lower leg and upper trunk. Surface electromyography revealed rhythmic synchronous discharges with 100-200 ms duration in the agonist and antagonist muscles at approximately 4 Hz. The jerk-locked back averaging, long latency reflexes, and somatosensory evoked potentials studies were normal. We report myoclonus due to radiculitis in a patient with Guillain-Barré syndrome.