Abstract: When administered orally at doses of 500 and 250 mg/kg, the polysaccharides isolated from pilose antler (PPA) was found to have anti-ulcer action in three experimental gastric ulcer models in rats, namely the stress-restraint ulcer, acetic acid and pyloric ligation induced ulcers, but the drug was ineffective in indomethacin induced ulcer. PPA could decrease the level of gastric acid and pepsin activity in the gastric juice. In addition, the polysaccharides were found to be able to inhibit the increase of gastric acid and to raise the content of PGE₂ in the gastric juice in rats treated with pentagastrin previously. But, no effects on the gastric acid and PGE₂ were found in rats treated with histamine and pilocarpin. However, when rats were treated with aspirin, PPA showed no effect on gastric acid and PGE₂. From the above results, it seems that the anti-ulcer action of PPA may be related to it's effect on the metabolism of PG. The polysaccharides may'bring about decrease of gastric acid secretion. Therefore, PPA could protect the gastric mucous membrane from injury.