To study the prevalence of polymorphic variants of CYP2C19 in residents of the Aktyubinsk region, in patients with acute coronary syndrome after percutaneous coronary intervention. We studied included 100 patients with documented acute coronary syndrome, whom stent has been implanted and double antiplatelet therapy (aspirin and clopidogrel) was administered (average age was 49.2). The control group was formed of 255 volunteers without clinical and electrocardiographic manifestations of ischemia, and cardiovascular disease (CVD). In groups of patients and volunteers, most of them were ethnic Kazakhs 67% and 72% respectively. Thus, about 30% of patients CYP2C19*1/*2 acute coronary syndrome who live in Aktobe (Aktobe residents) are under the threat of a possible occurrence of new cardiovascular events due to low sensitivity to clopidogrel. Our study confirms that CYP2C19 G (681A) genotype has impact on antiplatelet effect of clopidogrel. The peculiarity of our work lies in the fact that we were the first who conducted pharmacogenetic study in patients treated with clopidogrel with ACS/PCI in the region inhabited by persons of mixed Slavic and Kazakh nationality.