BACKGROUND: There are few literatures evaluating the association between cytotoxin-associated gene A (CagA) positive strains of Helicobacter pylori (HP) and the severity of coronary heart disease (CHD). This study was designed to investigate this association. METHODS: Medical and drug history of 112 consecutive patients who were candidate for coronary angiography were taken. Fasting blood samples were obtained to measure C-reactive protein (CRP), anti Helicobacter pylori immunoglobulin G (anti-HP IgG), anti-CagA antibody (Ab) and interlukine-6 (IL6). According to angiography reports, participants were divided into patients with mild (n = 69) and with sever CHD (n = 36). To measure the association between CagA positive strains of HP with the severity of CHD, multivariate logistic regression tests were used by adjusting age, sex, history of diabetes mellitus (DM), and/or dyslipidemia (DLP), and/or hypertension (HTN), CRP status and IL-6 level. RESULTS: The analysis was concluded on 105 subjects. HP infection and CagA Ab were not significantly higher compared to the patients with severe and mild CHD (P = 0.28 and P = 0.68, respectively). Colonization of CagA positive HP did not significantly associate with severity of CHD (OR 1.05, 95% CI 0.33-3. 39). CONCLUSION: Colonization of CagA positive HP was not an independent risk factor for severe coronary heart disease. Keywords: Helicobacter Pylori, CagA, Coronary Heart Disease, Severity </span