Allen’s Test is used to assess arterial sufficiency to the hand. To perform this test, ask the patient to clench her fist while you clamp down firmly on both the Ulnar and Radial Arteries. Once the patient has clenched her fist for a period of approximately 30 seconds, release one of the arteries. Return of colour to the hand indicates that the bloodflow is adequate for that arterial supply. You can repeat the test for the other artery.