Isolated cold stress testing is introduced as a method for quantification of thermoregulatory capacity of the upper extremities. Ninety-six patients with pain, numbness, or cold intolerance were studied. All diagnoses were confirmed by operation, arteriography, or dynamic radionuclide imaging. Patients were prospectively evaluated, and the observed response patterns were correlated with pathologic processes. Three characteristic temperature-response curves were identified. Isolated cold stress testing is a safe and effective technique that provides useful information about vasomotor tone and areas of arterial compromise and competency that is unavailable with static-state testing.