The term "branchial" should not lead to errors of interpretation and of classification. The essential points of normal embryology and comparative anatomy are reviewed: the special nature of the first entobranchial or spiracular pouch, the important role played in correlation by the second pouch, the general course of the two parts, external and internal, of the branchial apparatus and, finally, with regard to the latter, the problems posed by the development of lymphoid tissue in this region. The thyroglossal duct, although distinct from the branchial apparatus, remains in close relationship with it, in particular in the region of the hyoid where median cysts do not have an exclusively, thyroid origin. Amongst the lateral fistulae and cysts, the different types of which are described in relation to the tissue of their origin, the distinction must be drawn between two main types: those derived from the second pair of branchial pouches and those derived from the third entobranchial pouch only. It should be possible to recognise them on the basis of the characteristics described before operation, the latter being different in the two cases.