McArdle's disease is a disorder of carbohydrate metabolism, which is inhented as an autosomal recessive or occasionally an autosomal dominant trait. Hallmark of clinical features is exercise intolerence, I.e. muscle pain following strenuous exercise. Electrophysiologically insertion of an EMG needle shows that there is no electrical activity, differentiating this contracture from a muscle cramp. Histological examination of muscle biopsy specimen shows increase in glycogen and the presence of subsarcolemrnal blebs. We report a 23-year-old, male patient who presented clinical, electrophysiological, and histological findings compatible with McArdle's disease.