During the past year, we have employed the percutaneous femoral artery catheter technique for opacification of the renal arteries and for study of the aorta and the great vessels (Hemley, Arida and Ring, 1961). In two patients, in spite of excellent blood flow through the Seldinger needle upon insertion into the left femoral artery, it was impossible to pass the guide wire freely into the lumen of the aorta. After several attempts at manipulation of the wire, the procedure was abandoned on this side. Upon a second attempt on the right side in each of these patients, the procedure was accomplished without difficulty.