Progressive external ophthalmoplegia is a myopathic alteration of slow progression which affects the extrinsic ocular muscles; ptosis of the eyelid being the most characteristic sign. Nowadays, it is included as type of muscular dystrophy. Even though mitochondrial changes have been described, they are not specific to this disease. 2 cases are described in this paper, commenting on clinical, electromyographic and pathological aspects.