An 83-year-old woman was found unconscious several hours after she had fallen and fractured her lower limbs in a very cold cellar. On admission she was in shock and had metabolic acidosis, anemia and hypokalemia; her axillary and rectal temperature was 23 degrees C. Her initial ECG showed atrial fibrillation with slow ventricular response and a prominent J wave on the left precordial leads. These changes reverted to normal when body temperature returned to 37 degrees C. Moreover a transient, hypothermia-associated increase of QRS voltage was noted.