  The scattering theory approach makes it possible to carry out exact
calculations of Casimir energies in any geometry for which the scattering
T-matrix and a partial wave expansion of the free Green's function are
available. We implement this program for the case of a perfectly conducting
elliptic cylinder, thereby completing the set of geometries where
electromagnetic scattering is separable. Particular emphasis is placed on the
case of zero radius, where the elliptic cylinder reduces to a strip.
