Aneurysms in infants and children are rare and are usually associated with cardiovascular malformations or connective tissue disorders. A new subgroup of patients has become recognized over the past two decades--those with aneurysms associated with umbilical artery catheterization. Critically ill newborns who have required umbilical artery catheterization and have developed sepsis, usually staphylococcal, are at risk for the development of mycotic aneurysm disease of the aorta or its major branches or both. Since first described in 1970, 34 cases have been reported in the literature, 14 involving the descending thoracic aorta, 10 the abdominal aorta, 6 the iliac arteries, and 4 either the thoracoabdominal aorta or multiple aneurysms involving both the thoracic and abdominal aorta. This report presents a case we recently treated of a 15-month-old-boy with a large thoracoabdominal aortic aneurysm and aneurysms of the infrarenal abdominal aorta and proximal right common iliac artery. It includes a review of the recent literature to analyze pathogenesis, clinical manifestations, and to formulate methods of treatment.