We report a case of chronic progressive external ophthalmoplegia with pituitary hypothyroidism. This patient had complained of hearing-loss at the age of fourteen and loss of body weight at fifteen. She was examined by otorhinolaryngologists at large hospitals yearly over a period of 5-6 years, but hearing-loss remained unknown. As her ophthalmoplegia progressed (as is evident from family photographs from the age of sixteen onward), with hindsight it should have been recognized. When examined on October 11, 1991, she complained of ptosis, speech disturbance and dysphagia at the age of thirty-four. Neurological examination revealed limitation of ocular movement, bilateral ophthalmoplegia, facial muscle atrophy, and weak gag reflex. She showed muscle atrophy in her neck including both sternocleidomastoid, major and minor rhomboid, girdle and distal parts of upper and lower extremities. Muscle biopsy of her biceps demonstrated ragged-red fibers, cytochrome c oxidase (CCO) deficient fibers and deletion of mitochondrial DNA. A plain CT scan revealed bilateral periventricular lucency, and a brain MR image showed a normal sized pituitary gland but diffuse high-signal intensities in the both periventricular white matter with proton density weighted and T2-weighted axial MR image. And also her electroencephalogram showed diffuse 7 Hz slow waves in all areas and increased slow waves by hyperventilation, and all waves from I to V of the auditory brain stem response disappeared. The effect of TRH on serum TSH secretion was not evident in this patient. This case was ascertained to be chronic progressive external ophthalmoplegia with pituitary hypothyroid function.