A comparative study of gastric secretion in rats with pyloric ligature according to either Shays' or Dais' methods was carried on, studying in both groups gastic acid and peptic secretions, mucous pepsinogen, and Na+, K+, and Cl-. The acid-peptic output as well as gastric Pu/g were greater in Dais' method. There were no changes regarding mucous pepsinogen when comparing both methods. Cl- and Na+ determinations showed minimal changes, whereas K+ showed no difference in both methods. We explain these modifications based on the difference in the secreted volume, since the acid concentration and Pu/ml are practically the same when comparing both methods.