AIM: To investigate the gastrin secreting cells (G cells) and the somatostatin secreting cells (D cells) of antral mucosa in rats at the ultrastructural level. METHODS: Revised immunoelectron microscopic technique was used to detect the G cells and D cells in rat antral mucosa through gastrin and somatostatin antibodies labeled by colloidal gold. Also the relevant quantitative analysis regarding the granular number of colloidal gold in G cells and in D cells was conducted. RESULTS: Immunological granules of colloidal gold were distributed in G cells and D cells. Gastrin labeled golden granules or somatostatin labeled ones presented mainly as lobation-like or island-like congeries. Most of the golden congeries were observed dissociated in cytoplasms of G cells or D cells, near the basement membrane. A few golden congeries were located in nuclei. The number of golden granules in one G cell was around 107.04 +/- 19.68 and was 83.36 +/- 17.58 in one D cell. CONCLUSION: Gastrin secreting granules are located in cytoplasms and nuclei of G cells, and somatostatin secreting granules both in cytoplasms and in nuclei of D cells. The number of golden granules can be quantitatively analyzed to determine the relative amount of gastrin secreting granules or somatostatin secreting granules.