This work is a contribution to the understanding of some diachronic and synchronic aspects of the grammatical relation Indirect Object hitherto not studied: (i) grammaticalization (from the 12th to the 21st century) of cross reference -double representation- of indirect object in the light of the theory of 'drift' of Henning Andersen
(ii) revision of the conceptualization of grammatical relations within functional linguistics, on one hand of Simon Dik, on the other of Michael Herslund. The study is based on a corpus of texts (2 mill. running words) of Peninsular and American Spanish, dating from the end of the 19th to the beginnings of the 21st century. All kinds of genres - written as well as spoken - have been studied.