Electronic Journal of Differential Equations, Vol. 2013 (2013), No. 248, pp. 1-19. Title: Electromagnetic transmission problems with a large parameter in weighted Sobolev spaces Author: Jorge Eliecer Ospino (Univ. del Norte, Barranquilla, Colombia) Abstract: We present an a priori estimate for an electromagnetic transmission problem in unbounded exterior domains in R^3. We consider Maxwell's equations in two sub-domains, the bounded interior representing a conducting material (metal) and the unbounded exterior representing an insulating material (air). The behavior of the solution at infinity is described by means of families of weighted Sobolev spaces, so-called Beppo-Levi spaces [11]. We prove the existence and uniqueness of the solution. Submitted June 15, 2012. Published November 15, 2013. Math Subject Classifications: 65N15, 35A35. Key Words: Electromagnetic transmission problem; weighted Sobolev spaces; a priori estimates.