Among 189 consecutive cases with neuromyopathies, abnormalities of mitochondria in the muscles were seen in 5 cases. Ragged rad fibers (Rrf) were found with muscle biopsy with the use of staining of Gomory Trichrome. The ultrastructural abnormalities as revealed under the electron microscope in the mitochondria were as follows: 1. the mitochondria contained a lot of paracrystalline inclusion; 2. they were composed of lamellae; and 3., the mitochondria also showed dense spherical inclusions with abundant glycogen-rich sarcoplasm. The clinical manifestations of these patients consisted of: 1. muscular atrophy of various degrees. 2. muscular weakness of the proximal parts of the limbs, and 3. ptosis and ophthalmoplegia (in three cases). Three of the patients were treated with coenzyme Q10 with improvement of some of the symptoms and signs.