The opiate antagonist, naloxone, was injected for the reversal of hypotension due to Korean hemorrhagic fever, and the auihors observed changes in pituiiary hormones. In the hypotensive phase of the Korean hemorrhagic fever, the g-endorphin was high, and normal- ized granuaUy in the diuretic and conva1escent period. The naloxone raised the pulse rate and the blood pressure within 30 minutes without change in the central venous pressure. Around 30 minuted after the injection of the naloxone, the B-endorphin, ACTH and cortisol rose. The prolactin fell down 60 minutes after the naloxone injection.