BACKGROUND/AIMS: The aim of this study was to study the role of Helicobacter pylori infection and cagA expression in gastric carcinogenesis. METHODS: One hundred forty six patients were divided into three groups. Case group included 50 patients with gastric adenocarcinoma. Control group 1 included 38 patients with nongastric cancer, and control group 2 included 58 patients with nonulcer dyspepsia Biopsy specimens were evaluated to detect the presence of Helicobacter pylori by histology, rapid urease test and reverse transcription-polymerase chain reaction (RT-PCR) using primers specific for 16S rRNA and cagA mRNA of Helicobacter pylori. RESULTS: The expression rates of 16S rRNA and cagA mRNA of Helicobacter pylori in patients with gastric carcinoma were 74% and 51%, respecti vely. Although 90% of patients with gastric carcinoma had Helicobacter pylori infection, the signifi cant association between Helicobacter pylori infection and gastric carcinoma was not observed. There was no significant association between cagA expression and gastric carcinoma. CONCLUSIONS: Helico bacter pylori infection and cagA expression were not associated with the risk of gastric carcinoma.