Platelet-activating factor (PAF) has been shown recently to induce gastrointestinal damage similar to that evoked by endotoxin, suggesting that the autacoid could be implicated in other types of gastrointestinal damage. Thus, the effects of BN 52021 and BN 52063, two specific PAF antagonists, were investigated in various experimental models of gastrointestinal damage in rats. BN 52021 and BN 52063, markedly reduced both the PAF- and endotoxin-induced alterations of the mucosa, suggesting a role for the autacoid in the latter process. BN 52021 and another unrelated PAF antagonist, triazolam, partially reduced the restraint-stress-induced gastric damage in young female, but not male, rats. Similar partial protection was obtained in rats with ethanol-induced gastric damage. In contrast with atropine and ranitidine, BN 52021 did not affect the gastric hypersecretion in pylorus-ligated rats nor the aspirin-induced gastric ulcerations. The present results indicate that PAF plays a major role in the gastric damage induced by endotoxin and may also partially contribute to the gastric lesions induced by ethanol and stress. The results suggest that there is a potential therapeutic use for PAF antagonists in certain types of gastrointestinal lesions in man.