A supracondylar fracture of the humerus in a child, when widely displaced, can be complicated by dislocations of the brachial artery into the fracture line. Accompanied by the brachial veins and median nerve, the artery comes to lie posterior to the distal end of the proximal fragment of the humerus and to pass through the fracture site before resuming its normal situation anterior to the distal fragment of humerus. In this position, the artery is vulnerable and vasospasm or actual direct damage may occur on attempted manipulation of the frature. Characteristically, normal circulation of the extremity is presenst initially; but, on gentle manipulation or gentle long-axis traction, immediate brachial arterial insufficiency ensues. ln the patients presented adequate circulations returned when attempts at manipulation were stopped. It is recommended that, when faced with these clinical findings, exploration of the brachial artery through the antecubital space should be carried out.