AIM: To investigate the frequency of seropositivity aga- inst CagA, VacA proteins and to determine their indepen- dent effects on the development of duodenal ulcer (DU) in Turkish patients. METHODS: The study was designed as a prospective one from a tertiary referral hospital. Dyspeptic patients who were referred to our endoscopy unit for upper gas- trointestinal endoscopy between June 2003 and March 2004 and diagnosed to have DU or nonulcer dyspepsia (NUD) were included. Biopsies from the antrum and body of the stomach were taken in order to assess the current H pylori status by histology, rapid urease test and culture. Fasting sera were obtained from all patients and H pylori status of all sera was determined by IgG antibo- dies using an enzyme-linked immunosorbent assay (ELI- SA) kit. All seropositive patients were further analysed using Western blot assays detecting IgG antibodies aga- inst CagA and VacA proteins. The χ2 test was used for statistical comparison of the values and age-sex adjusted multiple regression analysis was used to determine the independent effects of CagA and VacA seropositivities on the development of DU. RESULTS: Sixty-three patients with DU and 62 patients with NUD were eligible for the final analysis. Seropositi- vity for anti-CagA was detected in 51 of 62 (82%), andin 55 of 63 (87%) patients with NUD and DU, respec- tively (p = no significance), and seropositivity for anti- VacA was found in 25 of 62 (40% ) and in 16 of 63 (25%) patients, with NUD and DU, respectively. CONCLUSION: These findings suggest that none of the- se virulence factors is associated with the development of DU in the studied Turkish patients with dyspepsia. AIM: To investigate the frequency of seropositivity aga- inst CagA, VacA proteins and to determine their independent effects on the development of duodenal ulcer (DU) in Turkish patients. METHODS: The study was designed as a prospective one from a tertiary referral hospital. Dyspeptic patients who were referred to our endoscopy unit for upper gas-trointestinal endoscopy between June 2003 and March 2004 and diagnosed to have DU or nonulcer dyspepsia (NUD) were included. Biopsies from the antrum and body of the stomach were taken in order to assess the current H pylori status by histology, rapid urease test and culture. Fasting sera were obtained from all patients and H pylori status of all sera was determined by IgG antibo- dies using an enzyme-linked immunosorbent assay (ELI-SA) kit . All seropositive patients were further analyzed using Western blot assays detecting IgG antibodies aga- inst CagA and VacA proteins. The χ2 test was used for statistical comparison of the values ​​and a sex-adjusted multiple regression analysis was used to determine the independent effects of CagA and VacA seropositivities on the development of DU. RESULTS: Sixty-three patients with DU and 62 patients with NUD were eligible for the final analysis. Seropositi- vity for anti Patients with NUD and DU, respecively (p = no significance), and seropositivity for anti-VacA was found in 25 of 62 (82%), and in 55 of 63 40%) and in 16 of 63 (25%) patients, with NUD and DU, respectively. CONCLUSION: These findings suggest that none of the-virulence factors is associated with the development of DU in the studied Turkish patients with dyspepsia.