Platelets activation and aggregation play an important role in the pathogenesis of atherothrombotic disease and its most important complications such as coronary artery disease and myocardial infarction. In clinical practice it is well-known that, in spite of the documented presence of advanced atherothrombotic disease, only a subset of patients develops acute myocardial infarction during their life-course. The reasons for individual differences in susceptibility to MI are poorly understood. Subjects with hypercoagulability and an increased tendency to form blood clots may be at increased risk. However, this is difficult to assess in clinical practice, since we lack a unique and reliable laboratory marker of hypercoagulability. Moreover, functional tests evaluating concentration and function of blood coagulation proteins are often subjected to multiple transient interferences, e.g. due to the use of antithrombotic and anticoagulant agents or the presence of concomitant inflammation. Genetic polymorphisms with a documented functional effect on blood coagulation proteins may represent a useful diagnostic and prognostic tool. During the last decade the study of polymorphisms as a risk factor for coronary artery disease and myocardial infarction were given largely convincing results. It demonstrated that gene polymorphisms of hemostasis and especially their combined effects are a risk factor for coronary heart disease and its major thrombotic complication - myocardial infarction. Hemostasis as a complex phenomenon modulated by the interaction of multiple genetic factors that do not have predominant action. Polygenic approach as a tool to identify subject at increased risk of developing complications suggests that the simultaneous presence of multiple genetic variations with a weak but significant effect on the process of hemostasis can affect the risk of serious thrombotic complications and that the number of prothrombotic alleles correlates with the risk of myocardial infarction in patients with advanced atherothrombotic disease.