Thrombolysis has been very effective in reducing the morbidity and mortality from acute myocardial infarction. Serious adverse events are not uncommon, however. We describe a case in which a haemopericardium and tamponade developed in a patient with a history of recurrent idiopathic pericarditis and to whom streptokinase had been administered following a suspected myocardial infarction. The case highlights the need for caution in the administration of thrombolytics to patients with a documented history of pericarditis.