1. This study was designed to determine the antiulcerogenicity of esculine in various types of experimentally induced gastric ulcers in which the appearance of lesions is due to an ischemic process: cold-restraint stress and pylorus-ligated induced ulcers. 2. In the first experimental model, esculine (50 mg/kg) produced a significant diminution not only in the number of haemorrhagic stomachs (21.5% by 37.5% of the controls) but also in the ulcer index, U.I. (1.00 +/- 0.63, P less than 0.05). 3. When the mucosal damage was induced as a consequence of the pylorus-ligated gastric secretion, pretreatment of esculine (25 and 50 mg/kg) prevented the formation of gastric lesions (12.4 +/- 2.8, P less than 0.05 and 12.2 +/- 1.20, P less than 0.005), although it was less effective than ranitidine (2.8 +/- 1.8, P less than 0.025). However a significant reduction on the acidity with a dose of 25 mg/kg was observed (31.69 +/- 6.42, P less than 0.025). For the rest of the studied parameters: pepsin, histamine and Na and K electrolytes no differences with regard to the control groups were produced. 4. The effects of esculine on mucosal lesions produced by intragastric instillation of 1 ml of absolute ethanol, were also studied. In this model esculine did not show any protective effect and high U.I. values were obtained.