Background and aim: Peptic ulcer is considered an important public health problem and generally associated with complicated conditions such as bleeding and perforation. The aim of this study is to reflect the rate of oxidative damage in the body among patients with H. pylori positive peptic ulcer by measuring serum 8-hydroxy-2p-deoxyguanosine (8-OHdG) and its association with the level of bacterial endotoxin. Methods Patients applied to Harran University Gastroenterology Outpatient Clinic with dyspeptic complaints were enrolled in this study. According to gastrointestinal endoscopy findings, 43 patients with H.pylori positive peptiv ulcer patients and 43 healthy volunteers were included in this study. H.pylori diagnosis was detemined by H.pylori urea breath and stool antigen tests. Serum 8-OHdG and endotoxins were measued by ELISA. Results A total of 43 patients with peptic ulcer (13 females 30 males), 43 healthy individuals (16 females 27 males) ages (18- 70) years in the study. In biopsies taken endoscopically; Hp severity was mild in 19 patients (43.9%), moderate in 21 patients (48.5%), and severe in 3 patients (7.6%). 8-OHdG which has the potential to mark DNA damage level in serum samples of patients with H.pylori positive peptic ulcer, was compared with the healthy and patient group. It was observed that there was a statistically significant difference (p <0.01). In addition, a weak correlation was found between OHdG and endotoxin. Conclusion: Reactive oxygen species (ROS) produced due to increased endotoxin as a result of H. pylıori infection can attack nucleic acid in infected cells resulting in an increased in serum 8-OHdG level. H.pylori and its endotoxin had a significant in peptic ulcer pathogensis.