Background: The study was designed to evaluate the anti-ulcer effect of chitosan, misoprostol, and their combination on gastric ulceration induced by indometacin in rats. Methods and experimental design: Chitosan was prepared from shrimp shells waste products. Thirty rats were divided into 5 groups, 6 rats each. Rats in group 1 (control) were given solid sugar and distilled water for 3 days; group 2 were treated by indometacin (25mg/rat) ; group 3,4, and 5 were treated by misoprostol, chitosan, and by the combination chitosan and misoprostol respectively before treatment with indometacin. Blood were collected before sacrificing the animals and used for estimation of MDA, a marker of oxidative stress. The stomachs were prepared for estimating the total gastric area, ulcerated area, tissue MDA, mucin production as well as for histopathological examination. Results: Indometacin produced gastric ulcers, and increased the total gastric area in all animals. These effects were associated with a significant elevation of MDA levels in the blood and in stomach tissues, and a significant reduction in mucin production. Misoprostol, chitosan and their combination protected gastric mucosa since they significantly reduced ulcer index. Moreover, the observed anti-ulcer effect was more with the combination in comparison to monotherapy of misoprostol or chitosan. Treatments by misoprostol, chitosan and their combination before indometacin significantly reduced blood and tissue MDA levels and increased mucin production. Conclusion: Chitosan, misoprostol and their combination have gastroprotective effects against indometacin-induced gastric ulceration in rats.