It is generally accepted that the medial circumflex femoral artery nourishes about two-thirds to four-fifths of the femoral head. In order to study the arteries in the idiopathic ischemic necrosis of the femoral head in adults, selective medial circumflex femoral arteriography was performed on 24 affected hips and 14 normal hips. This method enabled the better visualization of the medial circumflex femoral arterial system than the conventional femoral or internal iliac arteriography. The affected hips showed similar vascular patterns compared to normal hips. Anastomoses between the ascending branch or the medial circumflex femoral artery and the gluteal arteries, however, were rarely found in the affected hips. In the affected hips, various pathologic changes were demonstrated angiographically mainly in the portion of the ascending branch and the retinacular arteries. The existence of some degree of vascular insufficiency of the femoral head was assumed. However, complete occlusion of the medial circumflex femoral artery and its main branches that might cause head necrosis was seldom observed.