Introduction: Mast cells play an important role in the development of atherosclerotic plaque. More detailed understanding of the mechanisms involving mast cells, which occur in atherogenesis allow us to interpret at fair value of phenomena related to clinical manifestations, perspective of early diagnosis, targeted therapy treatment and individual prognosis of patients with metabolic syndrome aggravated with advanced atherosclerosis. The manifestations of various types of atherosclerotic plaques in various types of arterial vessels in nowadays are incompletely characterized and the expression of markers specific to mast cells has not been fully investigated to date. In this study we aimed to analyze the hystotopografic distribution of mast cells and degree of their degranulation in different types of plaques, to analyze the different types of arterial vessels in patients with atherosclerosis and metabolic syndrome aggravated with atherosclerosis as well as set a goal to analyze the significance of mast cells expression and evolutionary regularities for diagnostic and prognostic prediction. Materials & Methods: We included 34 patients who died as a result of atherosclerosis (n = 17) and metabolic syndrome with atherosclerotic complications (n=17), from which were sampled in order cerebral aa., carotid aa., coronary aa., aorta (abdominal portion), renal aa., iliac and vertebral aa., sampled fragments were processed by standard techniques, and morphological classification of cases was based on macroscopic and histopatological pattern of sections stained with hematoxylin-eosin and histochemical methods - silver impregnation and orcein. Results: Mast cell expression was detected immunohistochemically with MCT (mast cell tryptase) and evaluation was based on density and intensity score reflected quantitatively, of the final product reaction on atheromatous plaques sections. The expression of mast cells was positive in most types of vessels observed better at the level of adventitia of plaque region, in plaque and subendothelial in the direct neighborhood of the plaque. Conclusions: A statistical correlation was determined to the type of plaque and partially with clinical data. Immunohistochemistry with anti-MCT is useful for determining mast cells in atherosclerotic plaque and directly reflects the enzymatic activity of mast cell proteases, many important pathogenetic links of atherogenesis in patients with metabolic syndrome. The obtained data can be considered a thorough substrate for further scientific researches to identify potential methods of early intravital diagnosis and therapeutic targets.