Pulmonary embolism (PE) is a common and potentially fatal disease. Death usually occurs before hospital admission or in the initial in-hospital phase. A number of clinical and instrumental findings have been associated with a high risk of adverse short-term clinical outcomes in patients with PE. Advanced age, concomitant cardiopulmonary disease, and haemodynamic instability, as well as large perfusion defects at lung scanning and acute right heart dysfunction as assessed by echocardiography, are associated with adverse in-hospital outcome. Elevated serum levels of troponin I have been recently demonstrated to be associated with severe right ventricular dysfunction and adverse in-hospital outcome in patients with PE. Early recurrence of PE is associated with a high mortality rate. Right heart dysfunction, as assessed by echocardiography and an acute fall in platelet count, have been suggested as risk factors for recurrence of PE. A reduction in mortality in the subgroup of patients with a poor prognosis might be achieved by using more aggressive treatments such as thrombolysis and surgical or interventional procedures. However, such treatments are invariably associated with bleeding and other procedural complications.