Noninvasive testing for patency and completeness of the palmar arch prior to radial artery (RA) harvesting for coronary revascularization is a frequently requested test in the Vascular Laboratory (VL). The sonographer and interpreting physician must be aware of palmar arch anatomy and common variations in order to provide accurate information and avoid hand ischemia. The RA is a favored conduit for coronary revascularization due to good early and mid-term patency rates, which are superior to vein grafts.(1) Cardiac surgeons need precise information on adequate ulnar artery (UA) collateral circulation prior to harvesting the RA to avoid hand ischemia. Since the reliability of the Allen's test is in dispute, noninvasive assessment in the VL is frequently utilized.