The Klippel-Trenaunay syndrome (KTS) is a congenital disorder resulting from a mesodermal abnormality, characterised by cutaneous capillary haemangiomas, hypertrophy of bone and soft tissues and varicose veins. The presence of intracranial aneurysms has rarely been described, while oesophageal duplication has not been reported previously. We describe a patient with the KTS with both there additional abnormalities, which could be explained by a postulated mosaic gene abnormality.