Introduction. Acute coronary syndrome is a collective concept that reflects any form of exacerbation of coronary heart disease from unstable angina to acute myocardial infarction. Modern principles for the diagnosis and treatment of this syndrome are coronary angiography and urgent stenting of the affected coronary artery. These patients, having survived a life-threatening condition and surgical treatment, have a high probability of acute erosive and ulcerative gastroduodenal lesions and dependent gastrointestinal lesions. As a result, conservative treatment of acute ulcers and erosions complicated by bleeding remains unsatisfactory, mortality ranges from 36.4 to 50-80%.The aim of the study was to evaluate effectiveness of the proposed measures to prevent erosive and ulcerative lesions of the stomach and duodenum and gastrointestinal bleeding in patients with acute coronary syndrome who underwent coronary artery stenting.Materials and methods. The study included 614 patients who underwent percutaneous coronary intervention and stenting of the arteries of the heart due to the development of acute coronary syndrome. The patients were divided into two groups. The first group included 284 patients treated in 2018. Prevention of acute erosive and ulcerative gastroduodenal lesions was not routinely performed in this group. The second group included 330 patients treated in 2019. All patients in this group underwent prophylaxis and included omeprozole 40 mg per day from the first hours of the patient's stay in the hospital.Results. During the entire study period, 31 patients died in the early and late postoperative period in the first group, 18 of them during the first hospitalization. In the second group, 35 patients died during the entire study period in the early and late postoperative period, 21 of them during the first hospitalization. With the development of gastrointestinal bleeding, the probability of a full recovery in a patient with acute coronary syndrome is extremely low, and the system of preventive measures avoids this problem.Conclusion. Prevention of stressful acute erosive and ulcerative gastroduodenal lesions due to use of intravenous proton pump inhibitors in increased dosages (omeprozole 40 mg per day) is indicated to the patients of the studied group; in the presence of additional risk factors, the prophylactic dosage of proton pump inhibitors is doubled (omeprozole 40 mg 2 times a day). Mandatory non-invasive diagnosis of Helicobacter pylori for all patients is also indicated; if the condition is detected, eradication therapy is to be carried out. It is also required to apply proton pump inhibitors for the entire period of dual antiplatelet or anticoagulant therapy.