Quazolast, a mast cell stabilizer, was evaluated for efficacy against acid independent (alcohol, HCl), or dependent (aspirin, indomethacin) gastric damage in rats. Its gastroprotective profile was compared to that of ranitidine. In addition, the antisecretory and gastric ulcer (acetic acid induced) healing capabilities of these agents were examined. Quazolast, in direct contrast to ranitidine, protected the rat gastric mucosa from acid-independent, but not acid-dependent gastric damage. Quazolast lacked antisecretory activity in rats; however, it did heal acetic acid induced gastric ulcers in this species. On day 15 after acetic acid injection, quazolast significantly healed such ulcers, while ranitidine did not. Although the exact mechanisms of gastroprotection and ulcer healing action for quazolast remain to be determined, it may be an effective agent for the treatment of gastric ulcers.