We report a case of Kearns-Shy syndrome in a 44-year-old woman. She complained of bilateral ptosis, exotropia and gait disturbance. Diffuse chorioretinal degeneration and numerous punctate whitish spots were observed in both fundi. Eye movements were severely disturbed. An electroretinogram was almost nonrecordable, while visually evoked cortical potentials to pattern stimulation were normal. The dark adaptation curve showed an elevation of rod threshold. Besides such ophthalmological findings, muscle weakness, extinguished tendon reflex and healing difficulty were observed. Blood lactate, pyruvic acid and serum creatinine kinase were at high levels. A muscle biopsy showed ragged-red fibers and partial deficiency of cytochrome c oxidase. The patient is being treated with coenzyme Q, and we are now following up the therapeutic effects of this treatment.