According to the data derived in the course of studying the allergological anamnesis and disease clinical picture, 70% of 241 patients with peptic ulcer manifested different allergic reactions. Elevation of IgE blood content recorded in 47% of 173 patients examined also attested to the high rates of allergization among this patients' population. Analysis of the prevalence of food and drug allergy among the 241 patients aged 16 to 65 years demonstrated the allergies to occur in 25 and 30% of patients, respectively. At the same time the food allergy was encountered more frequently among young patients aged 16-25 years, while the allergic reactions to the drugs were more typical for patients aged 50 to 65 years. About one-third of patients manifested the reactions to 2 or more different allergen groups (food, drug and others). The prevalence of different types of allergy in peptic ulcer patients increases with age. This particularly marks drug allergy which in the group of patients over 50 years occurred 3 times as often as in patients aged 16-25 years (in 54 and 19%, respectively). The data obtained suggest that polypharmacy which is almost permanently given to peptic ulcer patients is of paramount importance in the genesis of drug allergy, whereas the constitutional-hereditary and alimentary factors play the leading part in the genesis of food allergy.