The pathophysiology of Raynaud’s phenomenon (RP) remains an enigma. Whatever theories proposed, the final event leading to the clinical symptoms is the occlusion of digital vessels. However, the possibility that the upstream large arterial vessels contribute to vasopasm has never been investigated. We used a high resolution echo-tracking device to calculate lumen diameter, wall thickness, and circumferential wall stress upstream the digital arteries, i.e. at the site of the radial artery. Fifteen control women, 15 age-matched women with primary RP (PRP) and 15 women presenting with a secondary RP due to systemic sclerosis (SSc) were included in the study. All vasodilating agents were discontinued 72 h before the study session, which was conducted in a room with a stable ambient temperature of 22°C Radial artery internal diameter, intima-media wall thickness, and mean arterial pressure were measured simultaneously. Internal diameter of patients with RP was significantly decreased (p& < 0.001 vs. controls) whereas intima-media wall thickness and mean arterial pressure were closely similar in the three groups, resulting in an increase in the wall to lumen ratio. Thus, circumferential wall stress was significantly smaller (p& < 0.05 vs. controls) in patients with RP. In conclusion, this study demonstrates that in patients with RP, wall to lumen ratio is increased and circumferential wall stress is reduced at the level of the radial artery. It is suggested that the geometrical and mechanical changes of this artery may favor the downstream occlusive phenomena observed in patients with PRP and SSc.