Cardiac tamponade is an emergency situation. Diagnosis is to be suspected when an elevation of systemic venous pressure, a decline in systemic arterial pressure and a clinical context of neoplasia or recent acute pericarditis are associated. Transthoracic echocardiogram is the gold-standard of diagnosis, and allows the accurate diagnosis of a large pericardial effusion: precise localisation and haemodynamic evaluation are needed before therapeutic decision. Pericardiocentesis is the only appropriate treatment. Surgical procedure, or less traumatic echo-guided pericardiocentesis, provide rapid haemodynamic relief of symptoms. Prognosis is determined by aetiology.