BACKGROUND/AIMS: Helicobacter pylori (H. pylori) infects over half of world' s population and is associated with peptic ulcer disease. The age, sex, blood type O and smoking history are also known as the risk factors causing duodenal ulcer. The purpose of this study was to evaluate the relationship between these risk factors and histology of gastritis associated with H. pylori. METHODS: The study population consisted of 53 patients with endoscopically confirmed duodenal ulcer. The history of smoking was confirmed and ABO blood type was determined by slide agglutination. Two biopsy specimens were taken from the antrum during gastroscopy and were processed with routine H-E and alcian yellow-toluidine blue stain for grading of histologic finding and H. pylori colonization. The parameters (H. pylori colonization, neutrophil infiltration and the severity of chronic gastritis) tha could be assessed in a semi- quantitative fashion were graded on a scale ranging from 0 through 5 RESULTS: H. pylori infection was identified in 92% (49/53) of patients with duodenal ulcer. However the scoring of H. pylori gastritis was not different statistically according to age, sex, blood type and smoking. Chronic gastritis of smoker was significantly severer than that of non-smoker (p<0.05) CONCLUSIONS: We suggest that H. pylori infection is not correlated with age, sex, blood type and smoking in causing duodenal ulcer.