The protective effect of beef and pig collagen hydrolysates and their fractions were tested as anti-ulcerogenic agents in rats (weighing 250-350 g) against ulcerative lesions caused by ethanol. Beef and pig collagen hydrolysates were fractionated by ultrafiltration into different molecular weight fractions. The protocol employed a negative and a positive control and a single dose of the experimental samples given by intragastric intubation. The beef collagen did not present a dose-response correlation in the ethanol model, whereas pig collagen showed a logarithmic dose-response relationship. Beef collagen hydrolysate decreased the ulcerative lesion index of 55% versus a 61% decrease for pig collagen hydrolysate at the same dosage (750 mg/kg of body weight). No significant differences were found (P > .05) between the hydrolysates and their fractions.