The authors studied the possibilities of preventing intraventricular thrombosis (IVT) after acute myocardial infarction (AMI) by employing early therapeutical measures, and by checking the risk factors of IVT, and found a decrease in the IVT embolization potential through adequate therapy. They examined 200 patients with AMI, out of whom 30 [15%] were found to have IVT. According to the results obtained, the therapy of AMI by means of streptokinase had a prophylactic significance for preventing IVT [IVT occurrence - 10%]; a lesser preventive effect was provided by heparin with the 19% incidence of IVT, but the IVT occurred in 47% of patients without thrombolytic or anticoagulation therapy. The risk factors of statistical significance which led to IVT were apical aneurysm, anteroseptal and apical AMI, reduced left-ventricular ejection fraction and the female sex (p less than 0.05). A further IVT follow-up confirmed the risk of systemic artery embolization, especially in malignant IVT (p less than 0.01). In such cases, effective prevention seems to require anticoagulation therapy which must follow immediately after IVT diagnosis and continue up to 50% regression of the thrombus or to its total disappearance.