A patient with complete transposition and a ventricular septal defect was clinically improved by an atrial septectomy at nine years but continued sepsis in the thoracotomy scar resulted in blood-stream infection with Staphylococcus aureus at the age of 24 years. A deep nylon suture was found and removed at surgical exploration. Five months later she again became febrile and had a vasculitic skin rash which responded to antibiotic therapy. At that time she was cyanosed and had a restricted exercise tolerance and was found to have aneurysmal dilatation of the pulmonary trunk. A year later she had acute chest pain with increased breathlessness, fever, hepatomegaly and pulmonary regurgitation. The fever did not respond to antibiotic therapy and she died suddenly following removal of a Hickman line. At postmortem examination, there was found to be a false aneurysm in the mediastinum due to rupture of the aneurysmal pulmonary trunk. No evidence of infection was found and it was considered that the low grade pyrexia had been due to the large hematoma within the false aneurysm.