Klippel-Trenaunay syndrome (KTS) is a rare congenital, vascular disorder affecting one or more limbs. The syndrome is characterized by capillary malformations, soft tissue or bony hypertrophy and varicose veins or venous malformations. We present a case of this disorder in a twelve-year old boy who had an enlarged right lower limb with varicosities. Investigations revealed extensive superficial and deep venous varices, with dilatation of the right common iliac and external iliac veins. Klippel-Trenaunay syndrome should be suspected in a child presenting with capillary haemangioma and an enlarged limb.