Pulmonary arterial rupture due to the use of a Swan-Ganz catheter is a rare accident, with an estimated 2% incidence rate. It is fatal in almost 50% of cases. Predisposing factors are age greater than 60 years, pulmonary arterial hypertension and anticoagulant treatment. In patients older than 60 years, changes in the arterial wall increase the risk of rupture; pulmonary hypertension leads to too distal a movement of the catheter, and a concomitant treatment with anticoagulant drugs increases the amount of blood lost. Handling errors when setting up the catheter are often the cause of these accidents, especially a balloon too blown up and a catheter pushed too far. A subsequent movement of the catheter can be a cause of rupture during cardiac surgery. Haemoptysis is the major symptom of this accident, being found in 90% of cases. It can however be of minor importance; if it is ignored, this can lead to a secondary overwhelming haemorrhage. The haemorrhage can be life-threatening because of the cardiovascular collapse and acute respiratory failure by asphyxia. The treatment can only be carried out in intensive care. It will depend on the severity of the accident. It can go from an expectant wait after partial or total removal of the catheter, to an emergency thoracotomy for vascular suture, segmentectomy or even lobectomy. Intermediate measures include turning the patient onto the healthy side, injecting adrenaline or a clot of the patient's blood by the distal end of the catheter, placing a Fogarty catheter in the affected bronchus, or tracheal intubation with a double-lumen catheter and using mechanical ventilation with PEEP.(ABSTRACT TRUNCATED AT 250 WORDS)