Aim. To compare the sensitivity of detecting H. pylori in gastric biopsy and resection specimens using modified Giemsa stain and immunohistochemistry, using a commercially available anti-H. pylori antibody (Dako, Denmark). Methods. Gastric antral biopsy specimens showing chronic gastritis (28 cases) together with tissue blocks from gastrectomy specimens for duodenal ulcer (2 cases) were stained with modified Giemsa and immunoenzymatic alkaline phosphatase - anti-alkaline phosphatase (APAAP) method, and were carefully examined for the presence of H. pylori. Results. Using a modified Giemsa stain, the spiral shaped bacteria of H. pylori stained blue, were attached to the brush border of the gastric foveolar epithelial cells. However, the specificity of modified Giemsa stain depended on the morphological appearance of H. pylori. The specificity of immunostaining permitted detection of low numbers or even single organisms. In all cases bacteria were more prominent and easier to detect in immunostained preparations. H. pylori was identified in 22 (73.3%) of 30 sections stained with modified Giemsa stain, but it could be identified with greater frequency in sections stained with APAAP, in 27 (90%) of 30 sections. Conclusion. Immunohistochemical identification of H. pylori was better than Giemsa stain for detecting that organism.