The incidence of the post-myocardial infarction syndrome (Dressler's syndrome) among thrombolized patients has not been established yet. To clarify this issue we prospectively studied 201 consecutive patients with acute myocardial infarction who had undergone recombinant tissue-type plasminogen activator therapy followed by 5 days of heparin administration. All patients were followed for at least 3 months for clinical signs of Dressler's syndrome. None of the 148 patients (76%) who showed clinical signs of early reperfusion had Dressler's syndrome. The sole patient in the group who manifested the syndrome developed it 3 weeks following extensive anterior myocardial infarction with no evidence of reperfusion. Although 4 patients manifested signs of early pericarditis, none developed the syndrome. We conclude that Dressler's syndrome has in fact been rendered a rare phenomenon among patients who benefit from thrombolytic therapy.