A case of 25-year-old woman with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) was reported. She had short stature, episodic vomiting with headache, several episodes with homonymous hemianopsia, progressive intellectual decline, generalized convulsion, muscular atrophy, sensory disturbance on the left side of the body, and primary amenorrhea. Lactate, pyruvate and the lactate to pyruvate ratio were elevated in the serum and cerebrospinal fluid. Muscle biopsy revealed ragged-red fibers. On electron microscopy there were subsarcolemmal aggregations of abnormal mitochondria with proliferation of crista and inclusions. Activities of the respiratory chain enzymes of the muscle mitochondria were normal. She showed a failure of GH response to arginine and levodopa and delayed response of serum GH to growth hormone releasing factor (GRF). She also showed decreased gonadotropin levels and delayed response of the hormone to LH-RH. In this case, a dysfunction of the hypothalamo-pituitary axis may be related to the short stature and primary amenorrhea. It is suggested that the hypothalamo-pituitary hypofunction may be one of the characteristic features in MELAS.