During the fourth week the human embryo develops a group of five paired arches at the cranial end. These are the branchial arches, soon completed by the formation of four ectodermal invaginations or branchial clefts and four endodermal branchial pouches. These primary organs will mostly disappear; the remaining form the definite head and neck structures. The congenital persistance of abnormal tissue is at the origin of congenital neck anomalies known as branchial cysts or fistulae and the thyreoglossal cyst or fistula. The localisation and course of these fistulae based on their embryological origin are predictable. The diagnosis is essentially clinical. The treatment is early surgical resection.