Secondary Raynaud's phenomenon is the most common manifestation of systemic sclerosis, affecting more than 99% of systemic sclerosis patients, and a major cause of morbidity. Frequent and prolonged secondary Raynaud's phenomenon attacks not only cause severe discomfort and pain but also ischemic acral tissue damage. In addition to vasoactive drugs, carbon dioxide (CO 2) hand bath and hot water bath are potential non-pharmacological treatment options which can be self-administered by affected patients at any time. In order to compare the efficacy of these two physical measures, this randomized, clinical study evaluated the effects of a single CO 2 hand bath in patients with systemic sclerosis and secondary Raynaud's phenomenon and a healthy control group versus a single hot water hand bath on acral perfusion in systemic sclerosis by Doppler ultrasonography. None of the patients had currently digital ulcers, a vasoactive medication or a concomitant vascular disease. CO 2 immersion induced an acute hemodynamic response, whereas hot water immersion had no significant effect on acral perfusion in systemic sclerosis.