CENTRE DE MATHEMATIQUES APPLIQUEES C.M.A.P. Couplage Equations de Maxwell - Potentiels Retardes pour les Milieux Heterogenes (Suite) Toufic AbboudToni Sayah We are interested in the coupling of volumic Maxwell's equations and boundary integral equations for locally heterogeneous media in ${\R}^3$. We present two different variational formulations. Coerciveness properties are proven. That leads to existence, uniqueness and stability results. Finally, we discuss the practical influence of interior eigenvalues on the results. 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/1998 under the name abboud_sayah_380.mars.ps or by Netscape or any other www client via the CMAP www server http://www.cmap.polytechnique.fr