Helicobacter pylori causes various diseases such as chronic gastritis, peptic ulcer and gastric cancer. While majority of the people infected with H. pylori is asymptomatic, 15-20 % of them develop such diseases. The main factors, which determine the development of H. pylori related diseases might be bacterial virulence, host genetic and environmental factors. The aim of this study was to reveal the factors that play a role in the disease development in patients with refl ux esophagitis and peptic ulcer, infected with Helicobacter pylori. Environmental factors such as medical agents, smoking and body mass index were evaluated. The factors specic to bacteria such as vacA, CagA, babA and iceA virulence genotypes and the host factors such as IL-1, IL-2, IL-4, IL-6, IL-10, IL-12, interferon-γ, TNF-α, ve TGF-ß1 gene polymorphisms were compared between the two groups. H. pylori infected twenty five patients with refl ux esophagitis and peptic ulcer were enrolled in the study. There was no statistical difference between the two groups regarding environmental factors. IL-2 -330T +166T (p=0.037) and IL10 -1082A; -819C (p=0.049) gene polymorphisms were significantly more common in the group of patients with peptic ulcer compared to the group with refl ux esophagitis. In both groups of patients, either with refl ux esophagitis or peptic ulcer, multiple H. pylori virulence genotypes (cagA, vacA, babA) (mean values 74 %, 78 %, 54 % respectively) were observed. In this study, we revealed that cytokine gene polymorphisms may play a role in the development peptic ulcer while H. pylori virulence genotypes seem to be crucial for the development of associated diseases.