Background. Endothelioprotectors (EP) are a group of drugs with different pathogenetic mechanisms of action that prevent disruption and/or restore the structural and functional properties of vascular endothelium. EP are mainly used in the treatment and prevention of cardiovascular and cerebrovascular diseases and their complications. Objective. To describe the role of EP in modern therapy of vascular diseases on the example of L-arginine (Tivortin, “Yuria-Pharm”). Materials and methods. Analysis of literature data on this topic. Results and discussion. The endothelium can be considered as a separate organ that regulates the work of blood vessels. Nitric oxide (NO) is the main signaling molecule of the endothelium. In humans, NO is produced from L-arginine. The latter is a conditionally essential amino acid, which means that it is synthesized in sufficient quantities only in perfectly healthy adults. Arginine is practically not synthesized in children under 5 years of age and in persons over 50 years of age. The main food sources of arginine are meat (pork, poultry), chocolate, soybeans, however, nutrition may not always provide the necessary need for L-arginine. The effects of NO include decreased intracellular calcium, smooth muscle cell relaxation, and vasodilation. As a result, the total peripheral vascular resistance and blood pressure decrease. One of the leading negative factors affecting the heart and blood vessels is hypercholesterolemia, which disrupts the production and release of NO. An improvement in endothelium-dependent vasodilation and a reduction in the size of atherosclerotic plaques with L-arginine have been demonstrated in a rabbit model with hypercholesterolemia. Endothelial dysfunction is an important concept in modern cardiology and medical science. Its main manifestation is a decrease in the NO bioavailability, so in order to eliminate endothelial dysfunction, EP are prescribed. The ideal EP should have such properties as a pronounced cardio- and cerebroprotective effect, rapid onset of action, no side effects, and low cost. L-arginine (Tivortin) is one of the best known EP. It can be used in the treatment of chronic heart failure to increase exercise tolerance. Tivortin supplies the depleted endothelium with a substrate for NO synthesis, facilitating cell function. Tivortin can be used not only in cardiological patients. The research of V.V. Bezugla et al. (2017) showed that Tivortin aspartate for oral administration improves the general and special performance of athletes in cyclic and strength sports, as well as reduces the severity of psychophysiological stress. In addition, the neuro-rehabilitation properties of Tivortin are demonstrated, which justifies its feasibility in the treatment and prevention of stroke. In the study of M.M. Sunychuk et al. (2014) the inclusion of Tivortin (100 ml infusion once a day from the 4th day after stroke for 10-14 days) in the complex therapy contributed to a more positive dynamics of assessments on the NIHSS, Bartel and Rankin scales than the use of standard therapy only. Improvement of the cerebral blood flow with the use of Tivortin is shown in other scientific papers (Mankovsky B.N. et al., 2014). The beneficial effect of L-arginine on the course of hypertension has also been proven (West S.G. et al., 2005). Studies conducted at the Department of Pharmacology and Clinical Pharmacology of the Dnipropetrovsk Medical Academy confirmed the cardiotropic and vasotropic properties of L-arginine. Conclusions. 1. NO – the main signaling molecule of the endothelium – is produced from L-arginine, the production of which almost stops after 50 y. o. 2. EP supply the endothelium with a substrate for NO synthesis, facilitating its function. 3. L-arginine (Tivortin, “Yuria-Pharm”) improves clinical, laboratory and functional parameters in patients with cardiovascular and cerebrovascular diseases.