Trichosanthes cucumerina Linn. (cucurbitaceae) is widely used in Indian folk medicine for varietyof disease conditions. The aim of present study was to evaluate the antiulcer activity of 50%ethanolic extract of fruits of Trichosanthes cucumerina Linn. (TCFE) using various experimentalmodels of gastric and duodenal ulceration in rats. Oral administration of 50% ethanolic extract offruits of Trichosanthes cucumerina Linn. was evaluated in rats against ethanol, aspirin and pylorusligated gastric ulcers as well as cysteamine-induced duodenal ulcers. In all the models studied,the antiulcer activity of TCFE compared with that of cimetidine (100 mg/kg, p.o.), an H2 receptorantagonist. TCFE showed significant antiulcer activity in ethanol-induced and aspirin-inducedgastric ulcer models. In 19 h pylorus ligated rats, significant reduction in ulcer index, total acidityand pepsin activity was observed with TCFE, when compared with the control group. Mucosaldefensive factors such as pH, mucin activity and gastric wall mucous content was found to beincreased with TCFE. TCFE was also, afforded remarkable protection in cysteamine-inducedduodenal lesions. The antiulcer activity of TCFE was comparable with that of cimetidine. Thus,TCFE possess significant antiulcer activity against both gastric and duodenal ulcers in rats. Theantiulcer activity may be attributed to its cytoprotective action and inhibition of acid secretaryparameters.