The placement of a central venous catheter is associated with specific risks including malposition of the catheter. We report the case of a 32 year old man who suffered from a severe thoracic trauma including haematopneumothorax on his left side. In the emergency room a large-bore central venous catheter was placed in the left subclavian vein, after blood had been aspirated successfully. Later, the haemodynamic state of the patient deteriorated, so that cardiopulmonary resuscitation had to be started. While great amounts of blood transfusions were applied via the catheter using a rapid transfusion device, the blood loss over the left sided chest tube increased rapidly. Emergency thoracotomy was performed, revealing that the catheter was not in intravenous position, but in intrapleural malposition. Haematothorax was caused by a laceration of the upper lobe of the left lung with severe bleeding from great vessels. This case shows that successful aspiration of blood does not exclude malposition of a central venous catheter. Correct position of the catheter must be verified using appropriate methods including chest X-ray, intracardiac ECG tracing or display of the central venous pressure curve on a monitor.