The aim of this study was to investigate the seroprevalence of Helicobacter pylori (HP) in patients with coronary atherosclerosis and acute coronary syndromes. We enrolled 152 patients (group I, 73 patients with acute coronary syndrome; group II, 79 patients with chronic stable angina) and 22 control subjects. An enzyme-linked immunosorbent assay for immunoglobulin (Ig) G test for HP diagnosis was used on all enrolled subjects. C-reactive protein (CRP) was also measured in all patients as an inflammatory marker. Seropositivity rates for HP were significantly higher in patients with coronary artery disease than in controls (80.2% versus 54.5%; P < 0.05). Although CRP level was significantly higher in group I than in group II (1.72 +/- A 2.89 mg/dl versus 0.53 +/- A 0.63 mg/dl, P < 0.0001), HP infection rates were similar between groups (86.3% versus 74.6%, P > 0.05). Infection with HP may influence atherogenesis through low-grade, persistent inflammatory stimulation. However, our data show evidence of increased systemic inflammation in patients with acute coronary syndrome, which was unrelated to an increased HP seropositivity.