AIM: To estimate the test characteristics of Heli- cobacter pylori (Hpylori) serology and of C14-urea breath test (C14-UBT) in two different peptic ulcer populations and in community controls. Second, the aim was to explore the association between the level of H pylori IgG antibodies and severity of inflammation as to active peptic ulceration in the same populations. METHODS: Vagotomized (n= 83), medically treated peptic ulcer patients (n=73) and one reference group of community controls (n=88) were gastroscoped. H pylori status was determined by histology, bacterial growth, C14-UBT and serology. Based on the updated Sydney System, cumulative scores from biopsies from the prepyloruos, incisura angularis, corpus and fundus were calculated. RESULTS: The prevalence of H pylori infection varied from 70% to 79%. The C14-UBT had high accuracycompared to the serology test. The sensitivity of the serology test was good, but the specificity was low (41%-71%). The association between H pylori IgG antibodies and scores of gastric mucosal inflammation and current or previous peptic ulcer were weak. CONCLUSION: The accuracy of C14-UBT to diagnose H pylori infection was good, and the clinical utility of a negative H pylori serology test was substantial, while the gain in clinical information of a positive test was meagre. Positive H pylori titres could not distinguish between subjects with or those without active peptic ulceration. AIM: To estimate the test characteristics of Heli-cobacter pylori (Hpylori) serology and of C14-urea breath test (C14-UBT) in two different peptic ulcer populations and in community controls. Second, the aim was to explore the association between the level of H pylori IgG antibodies and severity of inflammation as to active peptic ulceration in the same populations. METHODS: Vagotomized (n = 83), medically treated peptic ulcer patients (n = 73) and one reference group of community controls Based on the updated Sydney System, cumulative scores from biopsies from the prepyloruos, incisura angularis, corpus and fundus were calculated. RESULTS: The prevalence of Hpylori status was determined by histology, bacterial growth, C14-UBT and serology. The sensitivity of the serology test was good, but the specificity was low (41% -71%). The association between H pylori Ig G antibodies and scores of gastric mucosal inflammation and current or previous peptic ulcer were weak. CONCLUSION: The accuracy of C14-UBT to diagnose H pylori infection was good, and the clinical utility of a negative H pylori serology test was substantial, while the gain in clinical information of a positive test was meagre. Positive H pylori titres could not distinguish between subjects with or those without active peptic ulceration.