Three male patients with purulent pericarditis, in whom complete drainage could not be obtained by pericardiocentesis, were treated with transcatheter intrapericardial urokinase to prevent the development of chronic constrictive pericarditis. As shown by echocardiography, the intrapericardial fibrin layers disappeared in two cases and were reduced by more than half in the third. Effects on systemic coagulation indices and complications related to intrapericardial lysis were not observed.