Lyophilized aqueous extracts obtained from Agave americana L (Agavaceae) collected in the north of Sardinia were characterized with regard to their steroidal sapogenin content. Extracts of A. americana and genins isolated from them were evaluated for anti-inflammatory properties by testing their effects on carrageenin-induced edema. The effect of orally administered genins on gastric mucous membranes was also assessed. Lyophilized extracts administered by the intraperitoneal route at doses equivalent to 200 and 300 mg/kg of fresh plant starting material, showed good anti-inflammatory activity. Doses of genins (total steroidal sapogenins, hecogenin and tigogenin) equivalent to the amount in the lyophilized extracts produced an antiedentatous effect which was much stronger and more efficacious than that obtained with an i.p. administration of 5 mg/kg of indomethacin or dexamethasone 21-phosphate at a dose equivalent to the molar content of hecogenin administered. At the doses used to evaluate the anti-inflammatory activity, the genins did not have any harmful effect on the gastric mucous membranes. Lesions occurred when significantly higher doses of hecogenin were given, but gastric damage was still less than that caused by the drugs used for comparative purposes.