Occurrence of ulcerous lesions of gastric mucosa induced by the therapy with nonsteroidal anti-inflammatory drugs remains a widespread problem. Application of up-to-date drugs used for prevention of these disorders is often associated with undesirable side effects, so the new agents possessing gastroprotective effects should be found and studied. The aim of this study was to estimate the preventive influence of low esterified pectin and calcium pectate on indomethacin induced gastric mucous injury in rats. Both substances were given to animals for 8 days daily in the doses of 10, 25 and 50 mg kg-1 before indomethacin administration. The results showed that pectin substances used in the doses 25 and 50 mg kg-1 suppress formation of the gastric mucosa lesions. In groups of rats preliminary given low esterified pectin the total number of lesions was 52.5 and 43.9% lower then in the control group depending on the dose of polysaccharide. In rats given calcium pectate the total number of lesions was 45.2 and 51.6% lower, then in the control. In relation to the ulcer size, advance administration of polysaccharides particularly prevented formation of small spot ulcers. Therefore, we can conclude that pectin substances may be used as prophylactic agents for regular NSAID users.