From November 1993 to October 1994, a total o-f 71 patients with chronic dyspepsia were investigated -for the presence of Helicobacter pylori in their gastric antral biopsies by bacteriological and histological methods. Serum samples of those 71 patients in addition to 50 apparently healthy population were examined -For the presence o-f H. pylori antibodies. Clinical history, assessment of endoscopical examination were done for all patients, and two antral biopsies were taken from each patient. For the diagnosis of H.pylori infection, 3 methods were used: 1-bacteriological method: includes, direct Gram stain, biopsy urease test and culture of the biopsy material. 2-histological method: includes H?E to assess severity of gastritis and Siemsa stain to demonstrate H • pjyjjg r.i, in tissue secti ons. 3-serological method: includes, home-made IgB Dot-Blot ELISA and the commercial Pyloriset Latex agglutination tests to detect antibodies against H.pylori. The organism was diagnosed by Bram stain in 98.24% of the infected patients, by Giemsa stain in 89.477., by culture in 71.927. and by biopsy urease test in 85.967. of the infected patients. Data indicated that direct Gram stain is the most sensitive test for the diagnosis of H.pylori infection. Microbiological methods were superior to histological methods in diagnosing the infection and combined tests (culture and direct Gram's stain, Giemsa stain and biopsy urease test) were more satisfactory for the diagnosis of H.pylori status than using any single test of the present study. The IgG Dot-Blot ELISA test prepared by using sonicated bacteria and acid glycine extract as antigen demonstrated 89.04% sensitivity and 50% specificity in detecting the presence of H-Pylori infection, whereas the commercial Latex agglutination test was inferior in sensitivity (75.43%) but had the same specificity (50%). Therefore, Dot-Blot ELISA could be employed in epidemiological studies for screening the H.pylori status. H.pylori infection was found in 80.28% of the presented patients. In 83.58% of patients with histological gastritis, in 63.15% of those with chronic gastritis and in 91.66% of those with active chronic gastritis. The organism was diagnosed in 82.6% of duodenal ulcer patients, in 50% of gastric ulcer patients, and in 83.33% of patients with non-ulcer dyspepsia. Alcohol consumption, smoking, positive family history, sex, blood group and social class have no significant relation with the presence of H.pylori_ infection.