We report the case of a 48-year-old man who presented with left calf hypertrophy 6 years after an episode of left S1 sciatica related to a herniated disk. Magnetic resonance imaging disclosed muscle hypertrophy. Electromyography showed left S1 radiculopathy with abnormal spontaneous muscle activity. Neurogenic muscle hypertrophy is a rare phenomenon that is chiefly seen when denervation occurs slowly and gradually. The typical patient is a middle-aged man who has a history of S1 radiculopathy. The soleus muscle is the main site of involvement. The pathophysiology is unclear but may involve type I fiber hypertrophy in response to the complex repetitive discharges recorded by electromyography. The natural history of neurogenic muscle hypertrophy is incompletely understood.