A 52-year-old woman with a history of a hearing disturbance since age 20 experienced visual hallucinations and convulsions, followed by right hemiparesis and aphasia. On the basis of a muscle biopsy and mitochondrial DNA analysis, she was diagnosed as mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). This case is unique in that the stroke-like episodes occurred 30 years after disease onset.