The gastric pathogen Helicobacter pylori(H. pylori) establishes long-term chronic infection that can lead to atrophic gastritis, intestinal metaplasia, and gastric cancer. H. pylori, which express cytotoxic genes is now recohnized as a cause of peptic ulcer and is also a major risk factor for the development of gastric adenocarcinoma. We performed this study 1) to assess the detection rate of H. pylori according to direct investigation of bacteria of gastric biopsy specimen and two serologic tests of GAP test and Helico blot 2.0 system in the symptomatic and non-symptomatic group 2) to evaluate and compare the efficacy of two serologic tests of GAP test and Helico blot 2.0 system for the diagnosis of H. pylori infection. Forty-nine patients were positive for H pylori infection based on direct investigation of bacteria by histology. The detection rates of H. pylori infection based on direct investigation of bacteria by histology. The detection rates of H. phlori were significantly lower in gastric cancer than in other gastroduodenal disease(p<0.05). The concordance of two serologic tests of GAP test and Helico blot 2.0 system is poor. There was no statistically significant difference between the expression rate of CagA and VacA in the symptomatic and non-symptomatic group. Although Helico blot 2.0 system may not displace GAP test, it was a very sensitive serologic test for the diagnosis of H. pylori infection and it was used to detect IgG antibodies to H. pylori-specific antigens, including CagA, VacA and the various urease subunit. Our data suggest that further investigation is needed to determine whether or not the serologic expression of cytotoxic gene may be clinical usefulness of diagnostic methods in the gastroduodenal disease.