Rippling muscle disease (RMD) is a myopathy with hyperirritability, the pathophysiology for which is uncertain.We report electromyographic findings in a 30-year-old man with RMD. Clinical features included muscle rippling and percussion-induced rapid muscle contractions. Both were associated with bursts of short-duration, low-amplitude spikes, which resembled single muscle fiber discharges. Our case stands in contrast to previously reported cases, which showed either electrical silence or motor unit potential discharges associated with rippling, and may represent muscle fiber hyperexcitability. Muscle Nerve 43: 601–605, 2011