Raynaud's phenomenon is defined by an intermittent vasospasm of the arterioles of the distal limbs. Helicobacter pylori infection has been recently associated with Raynaud's phenomenon. The aim of this study was to assess the effects of H. pylori eradication on Raynaud's attacks. Forty-six patients affected by primary Raynaud's phenomenon were evaluated. H. pylori infection was assessed by [13C]urea breath test. Eradication therapy was given to infected patients for seven days. Discomfort and the duration and frequency of attacks of Raynaud's phenomenon per week were assessed. Thirty-six subjects were infected with H. pylori; the bacterium was eradicated in 83% of these after therapy. Attacks of Raynaud's phenomenon completely disappeared in 17% of the patients with H. pylori eradication. Discomfort and the duration and frequency of attacks of Raynaud's phenomenon were significantly reduced in 72% of the remaining patients. Conversely, attacks of Raynaud's disease did not change significantly during the 12-week follow-up period either in the H. pylori-negative patients or in the infected subjects in whom the bacterium was not eradicated by therapy. The study shows that H. pylori eradication causes a significant decrease in clinical attacks of Raynaud's disease. The reduction of vasoactive substances determined by the eradication of the bacterium may be the pathogenetic mechanism underlying the phenomenon.