A seventy-four-year-old woman with arteriosclerosis obliterans, diabetes mellitus, and hypertension was admitted for the treatment of intermittent claudication and coldness and pain in the right lower extremity. After the administration of a vasopressin V1 antagonist, OPC21268, the symptoms were markedly improved. Furthermore, blood flow in the dorsalis pedis artery and the cutaneous temperature in the right foot increased in response to acute and chronic administration of OPC21268. OPC21268 may be a new useful therapeutic tool for the treatment of arteriosclerosis obliterans.