Considering the high consumption rate of marjoram in the Iranian population, this study was designed to investigate the effects of marjoram extract on gastric acid and pepsin secretion. In this study, Wistar rats (n=12) were divided into two equal case and control groups. Under general anaesthesia with 50 mg/kg i.p. sodium thiopental, laparatomy was done and a cannula inserted in the duodenum. In the case animals marjoram (12.5 mg/kg) was injected into the stomach through the mentioned cannula. The gastric contents were collected by the wash-out technique. Acid and pepsin secretions were then measured by titration and the Anson method, respectively. In the marjoram group, basal acid and pepsin secretions were significantly increased compared with the control group (acid: 20+/-3.36 vs 4.1+/-0.36 micromol/15 min; pepsin: 9.04+/-0.01 vs 5.62+/-0.12 microg/15 min; p<0.001). In the control group, pentagastrin stimulation increased acid secretion in comparison with the basal level (10.14+/-1.34 vs 4.1+/-0.36 micromol/15 min, p<0.001), while in the marjoram group, there was a significant decline (16.46+/-3.23 vs 20+/-3.36 micromol/15 min, p<0.001). In the marjoram group pentagastrin increased pepsin secretion in comparison with the basal state (12+/-0.11 vs 9.04+/-0.1 microg/15 min, p<0.001). It seems that marjoram contains some components that activate chief and parietal cells and increase basal acid and pepsin secretion.