Since its first report in 1984 by Marshall and Warren, H. pylori has been recognized as the etiological agent of different gastric diseases such as gastritis ,chronic atrophic gastritis ,peptic ulcers and gastric cancer. The magnificent capabilities that H. pylori possessed ,by wide variety of virulence factors {ex. CagA , VacA , BabA, NAP, .etc}and strategies {ex. phase variation, immune modulation }, had create liaison via a long chain of events and processes between the organism and gastric mucosa that give eventually the different gastric diseases. many rings of this chain are invisible or intangible. This study was one of these efforts to obtain the unmitigated vista of this liaison. Aims of the study: a. To detect the expression of CagA cytotoxin on the gastric epithelial cells in patient with H. pylori gastritis by using In Situ Hybridization. b. Observe the differences in the levels of IL-8 expression, on the gastric epithelial cells between CagA positive and CagA negative H. pylori gastritis. c. Investigate the significance of p53and Bcl-2 immunoexpression in CagA positive and CagA negative gastric epithelial cells of H. pylori gastritis. Subjects and Methods : Patients undergoing oesophageal gastro-duodeno-scopy (OGD) in The Gastro-enterology Unit of AL-Kadhomyia Teaching Hospital in Baghdad from December 2006 to March 2007 were eligible for this study. Basing upon exclusion criteria thirty patients (19 male and 11 female) with a mean of age 39.47 years (range 16-70 years) were chosen. patients were presented with Antral Gastropathy, Gastritis, and/or chronic atrophic gastritis. Ten apparently healthy volunteers (7 male and 3 female) with the mean age 42.3 years and age range (17-63) years were enrolled as control. Multiple mucosal biopsy specimens were taken via sterile standard biopsy forceps from the site of lesion. One biopsy specimens were used for rapid urease test (RUT) for detection of H. pylori in tissue sample. Other biopsy specimens were fixed with 10% buffered formalin for preparation of paraffin embedded tissue sections. All selected patients give positive results in RUT. Then In Situ Hybridization was used to detect the presence of CagA and the expression of IL-8. Immunohistochemistry was used to demonstrate the immunoexpression of p53 and Bcl-2. Results: in the present study H. pylori was detected more frequently among (31-40)years age group. CagA had been detected in 70% of patients group. There was strong significant positive linear relationship (Pearson correlation Coefficient=0.794, p=0.000) between CagA positivity and p53 expression. and Significant positive linear relationship (Pearson correlation Coefficient=0.452 , p=0. 012)was found between CagA positivity and IL-8 expression. While ,there was negative linear relationship (Pearson correlation Coefficient=-0.240, p=0. 202) between CagA positivity and expression of Bcl-2. Conclusions: this study conclude that infection with CagA positive H. pylori strains leaded to high levels of IL-8 production from the gastric epithelium as well as over expression of p53 and down-regulation of Bcl-2 in these cells.