The aim of this study was to evaluate the association between the type of myocardial infarction (MI) and the circulating platelet aggregates [circulating aggregates of thrombocytes (CAT)]. The size of MI was assessed by the maximal values of creatine-kinase (CK). In 80 patients in the acute phase of MI the values of CAT and CK were manifold increased, mostly in 30 patients with anteroseptal MI (CAT 34.1 +/- 8.3%, CK: 920 +/- 340 IU), less markedly in 30 patients with inferior MI (CAT: 25 +/- 6.7%, CK: 739 +/- 263 IU) and in 20 patients with non-Q-wave MI (CAT: 20.7 +/- 1.9%, CK 518 +/- 224 IU). The differences between the groups were significant (p < 0.05). There was a significant linear correlation between CAT and CK in anteroseptal MI (r = 0.57, p < 0.01) and in inferior MI (r = 0.54, p < 0.01), but not in non-Q-wave MI (r = 0.15, p > 0.05). The results are concordant with the hypothesis that thrombotic event contributes more significantly to the pathogenesis of transmural acute myocardial infarction.