Pepsin K (chicken pepsin) in the test for hemoglobin proteolysis is 1.7 times superior to abomin (porcine pepsin) in the medium pH 2 and 44 times more potent in the medium pH 3. Even in pH 4 chicken pepsin retains its enzymatic activity while porcine pepsin in pH 4 looses its activity. These biochemical findings show that pepsin K is more effective in the treatment of enzymatic insufficiency of the stomach. Intake of 1-3 pepsin K tablets after meal for 4 weeks by 82 patients having chronic gastritis with secretory insufficiency was effective in 75% of patients.