Large Deviations and Variational Theorems for Marginal Problems February 1995 P. Cattiaux Ecole Polytechnique, CMAP, F-91128 Palaiseau Cedex and Universite Paris X equipe MODAL'X Nanterre 200 avenue de la republique F-92001 Nanterre Cedex. email: cattiaux@paris.polytechnique.fr and F.Gamboa Laboratoire de Statistiques Universit{e} Paris Sud F-91405 Orsay and Universit{e} Paris-Nord Institut Galil{e}e F-93430 Villetaneuse. email: gamboa@stats.matups.fr}} Summary: On a product Probability space , we give variational characterizations for the existence of a Probability measure Q with given marginals, such that Q is absolutely continuous with respect to P, and its density satisfies some integrability conditions. These characterizations, which are in some sense the dual formulation of a Theorem of Strassen , are obtained by using large deviations methods. We also study the minimal realizations of such Q. Key words: Marginal Problems-Large Deviations} The whole paper is available as a compressed Postscript file by internet procedure FTP anonymous on host barbes.polytechnique.fr ( 129.104.4.100) in the directory pub/RI/1995 under the name cattiaux_gamboa_315.fev.ps.gz or by Xmosaic or any other www client via the CMAP www server "http://blanche.polytechnique.fr/"