Thrombocytes participate in the pathogenesis of myocardial infarction. Larger platelets are more active than small ones. In patients after an acute coronary a larger number of platelets was found, a medium volume of půatelets and a similar thrombocytocrite as compared with the healthy population of comparable structure and age. The MPV in patients of advanced age is statistically significantly larger. There are no significant correlations between MPV and the risk factors investigated by the authors.